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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.

(PLATE 5. DIODON MACULATUS (DISTENDED AND CONTRACTED).)

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 18, 1832.

(PLATE 6. PELAGIC CONFERVAE.)

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. (1/8. M.
Montagne in "Comptes Rendus" etc. Juillet 1844; and "Annales des
Sciences Naturelles" December 1844.) 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 Plate 6
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 here add 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. (1/9. M. Lesson "Voyage de la Coquille" tome 1
page 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 (volume 2
page 239). To the references given by Peron may be added,
Humboldt's "Personal Narrative" volume 6 page 804; Flinder's
"Voyage" volume 1 page 92; Labillardiere, volume 1 page 287;
Ulloa's "Voyage"; "Voyage of the Astrolabe and of the Coquille";
Captain King's "Survey of Australia" etc.)

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 embedded: 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 direction of the bands
indicates 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 carcass 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 coinstantaneous 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 organised 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.

(PLATE 7. CATAMARAN (BAHIA).)





CHAPTER II.

(PLATE 8. BOTOFOGO BAY, RIO DE JANEIRO.)

Rio de Janeiro.
Excursion north of Cape Frio.
Great Evaporation.
Slavery.
Botofogo Bay.
Terrestrial Planariae.
Clouds on the Corcovado.
Heavy Rain.
Musical Frogs.
Phosphorescent Insects.
Elater, springing powers of.
Blue Haze.
Noise made by a Butterfly.
Entomology.
Ants.
Wasp killing a Spider.
Parasitical Spider.
Artifices of an Epeira.
Gregarious Spider.
Spider with an unsymmetrical Web.

RIO DE JANEIRO.

APRIL 4 TO JULY 5, 1832.



A few days after our arrival I became acquainted with an Englishman
who was going to visit his estate, situated rather more than a
hundred miles from the capital, to the northward of Cape Frio. I
gladly accepted his kind offer of allowing me to accompany him.

APRIL 8, 1832.

Our party amounted to seven. The first stage was very interesting.
The day was powerfully hot, and as we passed through the woods,
everything was motionless, excepting the large and brilliant
butterflies, which lazily fluttered about. The view seen when
crossing the hills behind Praia Grande was most beautiful; the
colours were intense, and the prevailing tint a dark blue; the sky
and the calm waters of the bay vied with each other in splendour.
After passing through some cultivated country, we entered a forest
which in the grandeur of all its parts could not be exceeded. We
arrived by midday at Ithacaia; this small village is situated on a
plain, and round the central house are the huts of the negroes.
These, from their regular form and position, reminded me of the
drawings of the Hottentot habitations in Southern Africa. As the
moon rose early, we determined to start the same evening for our
sleeping-place at the Lagoa Marica. As it was growing dark we
passed under one of the massive, bare, and steep hills of granite
which are so common in this country. This spot is notorious from
having been, for a long time, the residence of some runaway slaves,
who, by cultivating a little ground near the top, contrived to eke
out a subsistence. At length they were discovered, and a party of
soldiers being sent, the whole were seized with the exception of
one old woman, who, sooner than again be led into slavery, dashed
herself to pieces from the summit of the mountain. In a Roman
matron this would have been called the noble love of freedom: in a
poor negress it is mere brutal obstinacy. We continued riding for
some hours. For the few last miles the road was intricate, and it
passed through a desert waste of marshes and lagoons. The scene by
the dimmed light of the moon was most desolate. A few fireflies
flitted by us; and the solitary snipe, as it rose, uttered its
plaintive cry. The distant and sullen roar of the sea scarcely
broke the stillness of the night.

APRIL 9, 1832.

We left our miserable sleeping-place before sunrise. The road
passed through a narrow sandy plain, lying between the sea and the
interior salt lagoons. The number of beautiful fishing birds, such
as egrets and cranes, and the succulent plants assuming most
fantastical forms, gave to the scene an interest which it would not
otherwise have possessed. The few stunted trees were loaded with
parasitical plants, among which the beauty and delicious fragrance
of some of the orchideae were most to be admired. As the sun rose,
the day became extremely hot, and the reflection of the light and
heat from the white sand was very distressing. We dined at
Mandetiba; the thermometer in the shade being 84 degrees. The
beautiful view of the distant wooded hills, reflected in the
perfectly calm water of an extensive lagoon, quite refreshed us. As
the venda here was a very good one, and I have the pleasant, but
rare remembrance, of an excellent dinner, I will be grateful and
presently describe it, as the type of its class. (2/1. Venda, the
Portuguese name for an inn.) These houses are often large, and are
built of thick upright posts, with boughs interwoven, and
afterwards plastered. They seldom have floors, and never glazed
windows; but are generally pretty well roofed. Universally the
front part is open, forming a kind of verandah, in which tables and
benches are placed. The bedrooms join on each side, and here the
passenger may sleep as comfortably as he can, on a wooden platform
covered by a thin straw mat. The venda stands in a courtyard, where
the horses are fed. On first arriving, it was our custom to
unsaddle the horses and give them their Indian corn; then, with a
low bow, to ask the senhor to do us the favour to give us something
to eat. "Anything you choose, sir," was his usual answer. For the
few first times, vainly I thanked providence for having guided us
to so good a man. The conversation proceeding, the case universally
became deplorable. "Any fish can you do us the favour of giving
?" - "Oh no, sir." - "Any soup?" - "No, sir." - "Any bread?" - "Oh no,
sir." - "Any dried meat?" - "Oh no, sir." If we were lucky, by
waiting a couple of hours, we obtained fowls, rice, and farinha. It
not unfrequently happened that we were obliged to kill, with
stones, the poultry for our own supper. When, thoroughly exhausted
by fatigue and hunger, we timorously hinted that we should be glad
of our meal, the pompous, and (though true) most unsatisfactory
answer was, "It will be ready when it is ready." If we had dared to
remonstrate any further, we should have been told to proceed on our
journey, as being too impertinent. The hosts are most ungracious
and disagreeable in their manners; their houses and their persons
are often filthily dirty; the want of the accommodation of forks,
knives, and spoons is common; and I am sure no cottage or hovel in
England could be found in a state so utterly destitute of every
comfort. At Campos Novos, however, we fared sumptuously; having
rice and fowls, biscuit, wine, and spirits, for dinner; coffee in
the evening, and fish with coffee for breakfast. All this, with
good food for the horses, only cost 2 shillings 6 pence per head.
Yet the host of this venda, being asked if he knew anything of a
whip which one of the party had lost, gruffly answered, "How should
I know? why did you not take care of it? - I suppose the dogs have
eaten it."

Leaving Mandetiba, we continued to pass through an intricate
wilderness of lakes; in some of which were fresh, in others salt
water shells. Of the former kind, I found a Limnaea in great
numbers in a lake, into which the inhabitants assured me that the
sea enters once a year, and sometimes oftener, and makes the water
quite salt. I have no doubt many interesting facts in relation to
marine and fresh-water animals might be observed in this chain of
lagoons which skirt the coast of Brazil. M. Gay has stated that he
found in the neighbourhood of Rio shells of the marine genera solen
and mytilus, and fresh-water ampullariae, living together in
brackish water. (2/2. "Annales des Sciences Naturelles" for 1833.)
I also frequently observed in the lagoon near the Botanic Garden,
where the water is only a little less salt than in the sea, a
species of hydrophilus, very similar to a water-beetle common in
the ditches of England: in the same lake the only shell belonged to
a genus generally found in estuaries.

(PLATE 9. VAMPIRE BAT (Desmodus D'Orbigny). Caught on back of
Darwin's horse near Coquimbo. Head, full size.)

Leaving the coast for a time, we again entered the forest. The
trees were very lofty, and remarkable, compared with those of
Europe, from the whiteness of their trunks. I see by my notebook,
"wonderful and beautiful flowering parasites," invariably struck me
as the most novel object in these grand scenes. Travelling onwards
we passed through tracts of pasturage, much injured by the enormous
conical ants' nests, which were nearly twelve feet high. They gave
to the plain exactly the appearance of the mud volcanoes at
Jorullo, as figured by Humboldt. We arrived at Engenhodo after it
was dark, having been ten hours on horseback. I never ceased,
during the whole journey, to be surprised at the amount of labour
which the horses were capable of enduring; they appeared also to
recover from any injury much sooner than those of our English
breed. The Vampire bat is often the cause of much trouble, by
biting the horses on their withers. The injury is generally not so
much owing to the loss of blood, as to the inflammation which the
pressure of the saddle afterwards produces. The whole circumstance
has lately been doubted in England; I was therefore fortunate in
being present when one (Desmodus d'orbignyi, Wat.) was actually
caught on a horse's back. We were bivouacking late one evening near
Coquimbo, in Chile, when my servant, noticing that one of the
horses was very restive, went to see what was the matter, and
fancying he could distinguish something, suddenly put his hand on
the beast's withers, and secured the vampire. In the morning the
spot where the bite had been inflicted was easily distinguished
from being slightly swollen and bloody. The third day afterwards we
rode the horse, without any ill effects.

APRIL 13, 1832.

After three days' travelling we arrived at Socego, the estate of
Senhor Manuel Figuireda, a relation of one of our party. The house
was simple, and, though like a barn in form, was well suited to the
climate. In the sitting-room gilded chairs and sofas were oddly
contrasted with the whitewashed walls, thatched roof, and windows
without glass. The house, together with the granaries, the stables,
and workshops for the blacks, who had been taught various trades,
formed a rude kind of quadrangle; in the centre of which a large
pile of coffee was drying. These buildings stand on a little hill,
overlooking the cultivated ground, and surrounded on every side by
a wall of dark green luxuriant forest. The chief produce of this
part of the country is coffee. Each tree is supposed to yield
annually, on an average, two pounds; but some give as much as
eight. Mandioca or cassava is likewise cultivated in great
quantity. Every part of this plant is useful: the leaves and stalks
are eaten by the horses, and the roots are ground into a pulp,
which, when pressed dry and baked, forms the farinha, the principal
article of sustenance in the Brazils. It is a curious, though
well-known fact, that the juice of this most nutritious plant is
highly poisonous. A few years ago a cow died at this Fazenda, in
consequence of having drunk some of it. Senhor Figuireda told me
that he had planted, the year before, one bag of feijao or beans,
and three of rice; the former of which produced eighty, and the
latter three hundred and twenty fold. The pasturage supports a fine
stock of cattle, and the woods are so full of game that a deer had
been killed on each of the three previous days. This profusion of
food showed itself at dinner, where, if the tables did not groan,
the guests surely did; for each person is expected to eat of every
dish. One day, having, as I thought, nicely calculated so that
nothing should go away untasted, to my utter dismay a roast turkey
and a pig appeared in all their substantial reality. During the
meals, it was the employment of a man to drive out of the room
sundry old hounds, and dozens of little black children, which
crawled in together, at every opportunity. As long as the idea of
slavery could be banished, there was something exceedingly
fascinating in this simple and patriarchal style of living: it was
such a perfect retirement and independence from the rest of the
world. As soon as any stranger is seen arriving, a large bell is
set tolling, and generally some small cannon are fired. The event



Online LibraryCharles DarwinThe Voyage of the Beagle → online text (page 3 of 51)