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The Voyage of the Beagle

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
 
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