Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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From Several Well-Informed Persons, To Whom I Addressed Myself, I
Learned That There Are Calcareous Formations In The Great
Canary,
Forteventura, and Lancerota.* (* At Lancerota calcareous stone is
burned to lime with a fire made of the alhulaga, a
New species of
thorny and arborescent Sonchus.) I was not able to determine the
nature of this secondary rock; but it appears certain, that the
island of Teneriffe is altogether destitute of it; and that in its
alluvial lands it exhibits only clayey calcareous tufa, alternating
with volcanic breccia, said to contain, (near the village of La
Rambla, at Calderas, and near Candelaria,) plants, imprints of
fishes, buccinites, and other fossil marine productions. M. Cordier
brought away some of this tufa, which resembles that in the
environs of Naples and Rome, and contains fragments of reeds. At
the Salvages, which islands La Perouse took at a distance for
masses of scoriae, even fibrous gypsum is found.
I had seen, while herborizing between the port of Orotava and the
garden of La Paz, heaps of greyish calcareous stones, of an
imperfect conchoidal fracture, and analogous to that of Mount Jura
and the Apennines. I was informed that these stones were extracted
from a quarry near Rambla; and that there were similar quarries
near Realejo, and the mountain of Roxas, above Adexa. This
information led me into an error. As the coasts of Portugal consist
of basalts covering calcareous rocks containing shells, I imagined
that a trappean formation, like that of the Vicentin in Lombardy,
and of Harutsh in Africa, might have extended from the banks of the
Tagus and Cape St. Vincent as far as the Canary Islands; and that
the basalts of the Peak might perhaps conceal a secondary
calcareous stone.
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