Journ., Jan., 1830, p. 74; and April, 1830,
p. 258 - also Daubeny on Volcanoes, p. 438; and Bengal
Journ., vol.
Vii. p. 324.
[5] Political Essay on the Kingdom of New Spain, vol. iv.
p. 199.
[6] A similar interesting case is recorded in the Madras
Medical Quart. Journ., 1839, p. 340. Dr. Ferguson, in his
admirable Paper (see 9th vol. of Edinburgh Royal Trans.),
shows clearly that the poison is generated in the drying
process; and hence that dry hot countries are often the most
unhealthy.
CHAPTER XVII
GALAPAGOS ARCHIPELAGO
The whole Group Volcanic - Numbers of Craters - Leafless
Bushes Colony at Charles Island - James Island - Salt-lake in
Crater - Natural History of the Group - Ornithology, curious
Finches - Reptiles - Great Tortoises, habits of - Marine
Lizard, feeds on Sea-weed - Terrestrial Lizard, burrowing
habits, herbivorous - Importance of Reptiles in the
Archipelago - Fish, Shells, Insects - Botany - American Type
of Organization - Differences in the Species or Races on
different Islands - Tameness of the Birds - Fear of Man, an
acquired Instinct.
SEPTEMBER 15th. - This archipelago consists of ten
principal islands, of which five exceed the others in
size. They are situated under the Equator, and between
five and six hundred miles westward of the coast of
America. They are all formed of volcanic rocks; a few
fragments of granite curiously glazed and altered by the
heat, can hardly be considered as an exception. Some of
the craters, surmounting the larger islands, are of immense
size, and they rise to a height of between three and four
thousand feet. Their flanks are studded by innumerable
smaller orifices. I scarcely hesitate to affirm, that there
must be in the whole archipelago at least two thousand
craters. These consist either of lava or scoriae, or of finely-
stratified, sandstone-like tuff. Most of the latter are
beautifully symmetrical; they owe their origin to eruptions of
volcanic mud without any lava: it is a remarkable circumstance
that every one of the twenty-eight tuff-craters which
were examined, had their southern sides either much lower
than the other sides, or quite broken down and removed. As
all these craters apparently have been formed when standing
in the sea, and as the waves from the trade wind and the
swell from the open Pacific here unite their forces on the
southern coasts of all the islands, this singular uniformity
in the broken state of the craters, composed of the soft and
yielding tuff, is easily explained.
Considering that these islands are placed directly under
the equator, the climate is far from being excessively hot;
this seems chiefly caused by the singularly low temperature
of the surrounding water, brought here by the great southern
[map]
Polar current. Excepting during one short season, very
little rain falls, and even then it is irregular; but the clouds
generally hang low. Hence, whilst the lower parts of the
islands are very sterile, the upper parts, at a height of a
thousand feet and upwards, possess a damp climate and a
tolerably luxuriant vegetation. This is especially the case
on the windward sides of the islands, which first receive and
condense the moisture from the atmosphere.
In the morning (17th) we landed on Chatham Island,
which, like the others, rises with a tame and rounded outline,
broken here and there by scattered hillocks, the remains
of former craters. Nothing could be less inviting than the
first appearance. A broken field of black basaltic lava,
thrown into the most rugged waves, and crossed by great
fissures, is everywhere covered by stunted, sun-burnt brushwood,
which shows little signs of life. The dry and parched
surface, being heated by the noon-day sun, gave to the air
a close and sultry feeling, like that from a stove: we fancied
even that the bushes smelt unpleasantly. Although I diligently
tried to collect as many plants as possible, I succeeded
in getting very few; and such wretched-looking little
weeds would have better become an arctic than an equatorial
Flora. The brushwood appears, from a short distance, as
leafless as our trees during winter; and it was some time
before I discovered that not only almost every plant was
now in full leaf, but that the greater number were in flower.
The commonest bush is one of the Euphorbiaceae: an acacia
and a great odd-looking cactus are the only trees which
afford any shade. After the season of heavy rains, the islands
are said to appear for a short time partially green. The
volcanic island of Fernando Noronha, placed in many respects
under nearly similar conditions, is the only other
country where I have seen a vegetation at all like this of
the Galapagos Islands.
The Beagle sailed round Chatham Island, and anchored
in several bays. One night I slept on shore on a part of the
island, where black truncated cones were extraordinarily
numerous: from one small eminence I counted sixty of
them, all surmounted by craters more or less perfect. The
greater number consisted merely of a ring of red scoriae
or slags, cemented together: and their height above the plain
of lava was not more than from fifty to a hundred feet; none
had been very lately active. The entire surface of this part
of the island seems to have been permeated, like a sieve, by
the subterranean vapours: here and there the lava, whilst
soft, has been blown into great bubbles; and in other parts,
the tops of caverns similarly formed have fallen in, leaving
circular pits with steep sides. From the regular form of the
many craters, they gave to the country an artificial appearance,
which vividly reminded me of those parts of Staffordshire,
where the great iron-foundries are most numerous.
The day was glowing hot, and the scrambling over the rough
surface and through the intricate thickets, was very fatiguing;
but I was well repaid by the strange Cyclopean scene.
As I was walking along I met two large tortoises, each of
which must have weighed at least two hundred pounds:
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