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have been formed not like ordinary craters, but by a great and
sudden upheaval. There appear to me to be insuperable objections to
this view: on the other hand, I can hardly believe, in this and in
some other cases, that these marginal crateriform mountains are
merely the basal remnants of immense volcanos, of which the summits
either have been blown off or swallowed up in subterranean abysses.

From our elevated position we enjoyed an excellent view over the
island. The country on this side appears pretty well cultivated,
being divided into fields and studded with farm-houses. I was
however assured that of the whole land not more than half is yet in
a productive state; if such be the case, considering the present
large export of sugar, this island, at some future period when
thickly peopled, will be of great value. Since England has taken
possession of it, a period of only twenty-five years, the export of
sugar is said to have increased seventy-five fold. One great cause
of its prosperity is the excellent state of the roads. In the
neighbouring Isle of Bourbon, which remains under the French
government, the roads are still in the same miserable state as they
were here only a few years ago. Although the French residents must
have largely profited by the increased prosperity of their island,
yet the English government is far from popular.

MAY 3, 1836.

In the evening Captain Lloyd, the Surveyor-general, so well known
from his examination of the Isthmus of Panama, invited Mr. Stokes
and myself to his country-house, which is situated on the edge of
Wilheim Plains, and about six miles from the Port. We stayed at
this delightful place two days; standing nearly 800 feet above the
sea, the air was cool and fresh, and on every side there were
delightful walks. Close by a grand ravine has been worn to a depth
of about 500 feet through the slightly inclined streams of lava,
which have flowed from the central platform.

MAY 5, 1836.

Captain Lloyd took us to the Riviere Noire, which is several miles
to the southward, that I might examine some rocks of elevated
coral. We passed through pleasant gardens, and fine fields of
sugar-cane growing amidst huge blocks of lava. The roads were
bordered by hedges of Mimosa, and near many of the houses there
were avenues of the mango. Some of the views where the peaked hills
and the cultivated farms were seen together, were exceedingly
picturesque; and we were constantly tempted to exclaim "How
pleasant it would be to pass one's life in such quiet abodes!"
Captain Lloyd possessed an elephant, and he sent it half-way with
us, that we might enjoy a ride in true Indian fashion. The
circumstance which surprised me most was its quite noiseless step.
This elephant is the only one at present on the island; but it is
said others will be sent for.

MAY 9, 1836.

(PLATE 102. ST. HELENA.)

We sailed from Port Louis, and, calling at the Cape of Good Hope,
on the 8th of July we arrived off St. Helena. This island, the
forbidding aspect of which has been so often described, rises
abruptly like a huge black castle from the ocean. Near the town, as
if to complete nature's defence, small forts and guns fill up every
gap in the rugged rocks. The town runs up a flat and narrow valley;
the houses look respectable, and are interspersed with a very few
green trees. When approaching the anchorage there was one striking
view: an irregular castle perched on the summit of a lofty hill,
and surrounded by a few scattered fir-trees, boldly projected
against the sky.

The next day I obtained lodgings within a stone's throw of
Napoleon's tomb; it was a capital central situation, whence I could
make excursions in every direction. (21/1. After the volumes of
eloquence which have poured forth on this subject, it is dangerous
even to mention the tomb. A modern traveller, in twelve lines,
burdens the poor little island with the following titles, - it is a
grave, tomb, pyramid, cemetery, sepulchre, catacomb, sarcophagus,
minaret, and mausoleum!) During the four days I stayed here I
wandered over the island from morning to night and examined its
geological history. My lodgings were situated at a height of about
2000 feet; here the weather was cold and boisterous, with constant
showers of rain; and every now and then the whole scene was veiled
in thick clouds.

Near the coast the rough lava is quite bare: in the central and
higher parts feldspathic rocks by their decomposition have produced
a clayey soil, which, where not covered by vegetation, is stained
in broad bands of many bright colours. At this season the land,
moistened by constant showers, produces a singularly bright green
pasture, which lower and lower down gradually fades away and at
last disappears. In latitude 16 degrees, and at the trifling
elevation of 1500 feet, it is surprising to behold a vegetation
possessing a character decidedly British. The hills are crowned
with irregular plantations of Scotch firs; and the sloping banks
are thickly scattered over with thickets of gorse, covered with its
bright yellow flowers. Weeping-willows are common on the banks of
the rivulets, and the hedges are made of the blackberry, producing
its well-known fruit. When we consider that the number of plants
now found on the island is 746, and that out of these fifty-two
alone are indigenous species, the rest having been imported, and
most of them from England, we see the reason of the British
character of the vegetation. Many of these English plants appear to
flourish better than in their native country; some also from the
opposite quarter of Australia succeed remarkably well. The many
imported species must have destroyed some of the native kinds; and
it is only on the highest and steepest ridges that the indigenous
Flora is now predominant.

The English, or rather Welsh character of the scenery, is kept up
by the numerous cottages and small white houses; some buried at the
bottom of the deepest valleys, and others mounted on the crests of
the lofty hills. Some of the views are striking, for instance that
from near Sir W. Doveton's house, where the bold peak called Lot is
seen over a dark wood of firs, the whole being backed by the red
water-worn mountains of the southern coast. On viewing the island
from an eminence, the first circumstance which strikes one is the
number of the roads and forts: the labour bestowed on the public
works, if one forgets its character as a prison, seems out of all
proportion to its extent or value. There is so little level or
useful land that it seems surprising how so many people, about
5000, can subsist here. The lower orders, or the emancipated
slaves, are, I believe, extremely poor: they complain of the want
of work. From the reduction in the number of public servants, owing
to the island having been given up by the East India Company, and
the consequent emigration of many of the richer people, the poverty
probably will increase. The chief food of the working class is rice
with a little salt meat; as neither of these articles are the
products of the island, but must be purchased with money, the low
wages tell heavily on the poor people. Now that the people are
blessed with freedom, a right which I believe they value fully, it
seems probable that their numbers will quickly increase: if so,
what is to become of the little state of St. Helena?

My guide was an elderly man who had been a goatherd when a boy, and
knew every step amongst the rocks. He was of a race many times
crossed, and although with a dusky skin, he had not the
disagreeable expression of a mulatto. He was a very civil, quiet
old man, and such appears the character of the greater number of
the lower classes. It was strange to my ears to hear a man, nearly
white and respectably dressed, talking with indifference of the
times when he was a slave. With my companion, who carried our
dinners and a horn of water, which is quite necessary, as all the
water in the lower valleys is saline, I every day took long walks.

Beneath the upper and central green circle, the wild valleys are
quite desolate and untenanted. Here, to the geologist, there were
scenes of high interest, showing successive changes and complicated
disturbances. According to my views, St. Helena has existed as an
island from a very remote epoch: some obscure proofs, however, of
the elevation of the land are still extant. I believe that the
central and highest peaks form parts of the rim of a great crater,
the southern half of which has been entirely removed by the waves
of the sea: there is, moreover, an external wall of black basaltic
rocks, like the coast-mountains of Mauritius, which are older than
the central volcanic streams. On the higher parts of the island
considerable numbers of a shell, long thought to be a marine
species, occur imbedded in the soil. It proves to be a Cochlogena,
or land-shell of a very peculiar form; with it I found six other
kinds; and in another spot an eighth species. (21/2. It deserves
notice that all the many specimens of this shell found by me in one
spot differ as a marked variety from another set of specimens
procured from a different spot.) It is remarkable that none of them
are now found living. Their extinction has probably been caused by
the entire destruction of the woods, and the consequent loss of
food and shelter, which occurred during the early part of the last
century.

The history of the changes which the elevated plains of Longwood
and Deadwood have undergone, as given in General Beatson's account
of the island, is extremely curious. Both plains, it is said, in
former times were covered with wood, and were therefore called the
Great Wood. So late as the year 1716 there were many trees, but in
1724 the old trees had mostly fallen; and as goats and hogs had
been suffered to range about, all the young trees had been killed.
It appears also from the official records that the trees were
unexpectedly, some years afterwards, succeeded by a wire grass
which spread over the whole surface. (21/3. Beatson's "St. Helena"
Introductory chapter page 4.) General Beatson adds that now this
plain "is covered with fine sward, and is become the finest piece
of pasture on the island." The extent of surface, probably covered
by wood at a former period, is estimated at no less than two
thousand acres; at the present day scarcely a single tree can be
found there. It is also said that in 1709 there were quantities of
dead trees in Sandy Bay; this place is now so utterly desert that
nothing but so well attested an account could have made me believe
that they could ever have grown there. The fact that the goats and
hogs destroyed all the young trees as they sprang up, and that in
the course of time the old ones, which were safe from their
attacks, perished from age, seems clearly made out. Goats were
introduced in the year 1502; eighty-six years afterwards, in the
time of Cavendish, it is known that they were exceedingly numerous.
More than a century afterwards, in 1731, when the evil was complete
and irretrievable, an order was issued that all stray animals
should be destroyed. It is very interesting thus to find that the
arrival of animals at St. Helena in 1501 did not change the whole
aspect of the island, until a period of two hundred and twenty
years had elapsed: for the goats were introduced in 1502, and in
1724 it is said "the old trees had mostly fallen." There can be
little doubt that this great change in the vegetation affected not
only the land-shells, causing eight species to become extinct, but
likewise a multitude of insects.

St. Helena, situated so remote from any continent, in the midst of
a great ocean, and possessing a unique Flora, excites our
curiosity. The eight land-shells, though now extinct, and one
living Succinea, are peculiar species found nowhere else. Mr.
Cuming, however, informs me that an English Helix is common here,
its eggs no doubt having been imported in some of the many
introduced plants. Mr. Cuming collected on the coast sixteen
species of sea-shells, of which seven, as far as he knows, are
confined to this island. Birds and insects, as might have been
expected, are very few in number; indeed I believe all the birds
have been introduced within late years. (21/4. Among these few
insects I was surprised to find a small Aphodius (nov. spec.) and
an Oryctes, both extremely numerous under dung. When the island was
discovered it certainly possessed no quadruped excepting PERHAPS a
mouse: it becomes, therefore, a difficult point to ascertain,
whether these stercovorous insects have since been imported by
accident, or if aborigines, on what food they formerly subsisted.
On the banks of the Plata, where, from the vast number of cattle
and horses, the fine plains of turf are richly manured, it is vain
to seek the many kinds of dung-feeding beetles which occur so
abundantly in Europe. I observed only an Oryctes (the insects of
this genus in Europe generally feed on decayed vegetable matter)
and two species of Phanaeus, common in such situations. On the
opposite side of the Cordillera in Chiloe another species of
Phanaeus is exceedingly abundant, and it buries the dung of the
cattle in large earthen balls beneath the ground. There is reason
to believe that the genus Phanaeus, before the introduction of
cattle, acted as scavengers to man. In Europe beetles which find
support in the matter which has already contributed towards the
life of other and larger animals, are so numerous that there must
be considerably more than one hundred different species.
Considering this, and observing what a quantity of food of this
kind is lost on the plains of La Plata, I imagined I saw an
instance where man had disturbed that chain by which so many
animals are linked together in their native country. In Van
Diemen's Land, however, I found four species of Onthophagus, two of
Aphodius, and one of a third genus, very abundant under the dung of
cows; yet these latter animals had been then introduced only
thirty-three years. Previous to that time the kangaroo and some
other small animals were the only quadrupeds; and their dung is of
a very different quality from that of their successors introduced
by man. In England the greater number of stercovorous beetles are
confined in their appetites; that is, they do not depend
indifferently on any quadruped for the means of subsistence. The
change, therefore, in habits which must have taken place in Van
Diemen's Land is highly remarkable. I am indebted to the Reverend
F.W. Hope, who, I hope, will permit me to call him my master in
Entomology, for giving me the names of the foregoing insects.)
Partridges and pheasants are tolerably abundant; the island is much
too English not to be subject to strict game-laws. I was told of a
more unjust sacrifice to such ordinances than I ever heard of even
in England. The poor people formerly used to burn a plant which
grows on the coast-rocks, and export the soda from its ashes; but a
peremptory order came out prohibiting this practice, and giving as
a reason that the partridges would have nowhere to build!

In my walks I passed more than once over the grassy plain, bounded
by deep valleys, on which Longwood stands. Viewed from a short
distance, it appears like a respectable gentleman's country-seat.
In front there are a few cultivated fields, and beyond them the
smooth hill of coloured rocks called the Flagstaff, and the rugged
square black mass of the Barn. On the whole the view was rather
bleak and uninteresting. The only inconvenience I suffered during
my walks was from the impetuous winds. One day I noticed a curious
circumstance: standing on the edge of a plain, terminated by a
great cliff of about a thousand feet in depth, I saw at the
distance of a few yards right to windward, some tern, struggling
against a very strong breeze, whilst, where I stood, the air was
quite calm. Approaching close to the brink, where the current
seemed to be deflected upwards from the face of the cliff, I
stretched out my arm, and immediately felt the full force of the
wind: an invisible barrier, two yards in width, separated perfectly
calm air from a strong blast.

I so much enjoyed my rambles among the rocks and mountains of St.
Helena that I felt almost sorry on the morning of the 14th to
descend to the town. Before noon I was on board, and the "Beagle"
made sail.

On the 19th of July we reached Ascension. Those who have beheld a
volcanic island situated under an arid climate will at once be able
to picture to themselves the appearance of Ascension. They will
imagine smooth conical hills of a bright red colour, with their
summits generally truncated, rising separately out of a level
surface of black rugged lava. A principal mound in the centre of
the island seems the father of the lesser cones. It is called Green
Hill: its name being taken from the faintest tinge of that colour,
which at this time of the year is barely perceptible from the
anchorage. To complete the desolate scene, the black rocks on the
coast are lashed by a wild and turbulent sea.

The settlement is near the beach; it consists of several houses and
barracks placed irregularly, but well built of white freestone. The
only inhabitants are marines, and some negroes liberated from
slave-ships, who are paid and victualled by government. There is
not a private person on the island. Many of the marines appeared
well contented with their situation; they think it better to serve
their one-and-twenty years on shore, let it be what it may, than in
a ship; in this choice, if I were a marine, I should most heartily
agree.

The next morning I ascended Green Hill, 2840 feet high, and thence
walked across the island to the windward point. A good cart-road
leads from the coast-settlement to the houses, gardens, and fields,
placed near the summit of the central mountain. On the roadside
there are milestones, and likewise cisterns, where each thirsty
passer-by can drink some good water. Similar care is displayed in
each part of the establishment, and especially in the management of
the springs, so that a single drop of water may not be lost: indeed
the whole island may be compared to a huge ship kept in first-rate
order. I could not help, when admiring the active industry which
had created such effects out of such means, at the same time
regretting that it had been wasted on so poor and trifling an end.
M. Lesson has remarked with justice that the English nation would
have thought of making the island of Ascension a productive spot,
any other people would have held it as a mere fortress in the
ocean.

Near this coast nothing grows; farther inland an occasional green
castor-oil plant, and a few grasshoppers, true friends of the
desert, may be met with. Some grass is scattered over the surface
of the central elevated region, and the whole much resembles the
worse parts of the Welsh mountains. But, scanty as the pasture
appears, about six hundred sheep, many goats, a few cows and
horses, all thrive well on it. Of native animals, land-crabs and
rats swarm in numbers. Whether the rat is really indigenous may
well be doubted; there are two varieties as described by Mr.
Waterhouse; one is of a black colour, with fine glossy fur, and
lives on the grassy summit, the other is brown-coloured and less
glossy, with longer hairs, and lives near the settlement on the
coast. Both these varieties are one-third smaller than the common
black rat (M. rattus); and they differ from it both in the colour
and character of their fur, but in no other essential respect. I
can hardly doubt that these rats (like the common mouse, which has
also run wild) have been imported, and, as at the Galapagos, have
varied from the effect of the new conditions to which they have
been exposed: hence the variety on the summit of the island differs
from that on the coast. Of native birds there are none; but the
guinea-fowl, imported from the Cape de Verd Islands, is abundant,
and the common fowl has likewise run wild. Some cats which were
originally turned out to destroy the rats and mice, have increased,
so as to become a great plague. The island is entirely without
trees, in which, and in every other respect, it is very far
inferior to St. Helena.

One of my excursions took me towards the south-west extremity of
the island. The day was clear and hot, and I saw the island, not
smiling with beauty, but staring with naked hideousness. The lava
streams are covered with hummocks, and are rugged to a degree
which, geologically speaking, is not of easy explanation. The
intervening spaces are concealed with layers of pumice, ashes and
volcanic tuff. Whilst passing this end of the island at sea, I
could not imagine what the white patches were with which the whole
plain was mottled; I now found that they were sea-fowl, sleeping in
such full confidence, that even in mid-day a man could walk up and
seize hold of them. These birds were the only living creatures I
saw during the whole day. On the beach a great surf, although the
breeze was light, came tumbling over the broken lava rocks.

(PLATE 103. CELLULAR FORMATION OF VOLCANIC BOMB.)

The geology of this island is in many respects interesting. In
several places I noticed volcanic bombs, that is, masses of lava
which have been shot through the air whilst fluid, and have
consequently assumed a spherical or pear-shape. Not only their
external form, but, in several cases, their internal structure
shows in a very curious manner that they have revolved in their
aerial course. The internal structure of one of these bombs, when
broken, is represented very accurately in Plate 103. The central
part is coarsely cellular, the cells decreasing in size towards the
exterior; where there is a shell-like case about the third of an
inch in thickness, of compact stone, which again is overlaid by the
outside crust of finely cellular lava. I think there can be little
doubt, first, that the external crust cooled rapidly in the state
in which we now see it; secondly, that the still fluid lava within
was packed by the centrifugal force generated by the revolving of
the bomb, against the external cooled crust, and so produced the
solid shell of stone; and lastly, that the centrifugal force, by
relieving the pressure in the more central parts of the bomb,
allowed the heated vapours to expand their cells, thus forming the
coarse cellular mass of the centre.

A hill formed of the older series of volcanic rocks, and which has
been incorrectly considered as the crater of a volcano, is
remarkable from its broad, slightly hollowed, and circular summit
having been filled up with many successive layers of ashes and fine
scoriae. These saucer-shaped layers crop out on the margin, forming
perfect rings of many different colours, giving to the summit a
most fantastic appearance; one of these rings is white and broad,
and resembles a course round which horses have been exercised;
hence the hill has been called the Devil's Riding School. I brought
away specimens of one of the tufaceous layers of a pinkish colour
and it is a most extraordinary fact that Professor Ehrenberg finds
it almost wholly composed of matter which has been organised; he
detects in it some siliceous-shielded, fresh-water infusoria, and
no less than twenty-five different kinds of the siliceous tissue of
plants, chiefly of grasses. (21/5. "Monats. der Konig. Akad. d.
Wiss. zu Berlin" Vom April 1845.) From the absence of all
carbonaceous matter, Professor Ehrenberg believes that these
organic bodies have passed through the volcanic fire, and have been
erupted in the state in which we now see them. The appearance of
the layers induced me to believe that they had been deposited under
water, though from the extreme dryness of the climate I was forced
to imagine that torrents of rain had probably fallen during some
great eruption, and that thus a temporary lake had been formed into
which the ashes fell. But it may now be suspected that the lake was
not a temporary one. Anyhow we may feel sure that at some former
epoch the climate and productions of Ascension were very different
from what they now are. Where on the face of the earth can we find
a spot on which close investigation will not discover signs of that
endless cycle of change, to which this earth has been, is, and will
be subjected?

On leaving Ascension, we sailed for Bahia, on the coast of Brazil,
in order to complete the chronometrical measurement of the world.
We arrived there on August 1st, and stayed four days, during which
I took several long walks. I was glad to find my enjoyment in
tropical scenery had not decreased from the want of novelty, even



Online LibraryCharles DarwinThe Voyage of the Beagle → online text (page 48 of 51)