Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 3 - By Alexander Von Humboldt And Aime Bonpland.
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The Enormous Masses Of Muriate Of Soda
Recently Thrown Up By Vesuvius,* (* The Ejected Masses In 1822 Were So
Considerable
That the inhabitants of some villages round Vesuvius
collected them for domestic purposes.) the small veins of that salt
which
I have often seen traverse the most recently ejected lavas, and
of which the origin (by sublimation) appears similar to that of
oligist iron deposited in the same vents,* (* Gay-Lussac on the action
of volcanoes in the Annales de Chimie volume 22 page 418.) the layers
of gem-salt and saliferous clay of the trachytic soil in the plains of
Peru and around the volcano of the Andes of Quito are well worthy the
attention of geologists who would discuss the origin of formations. In
the present sketch I confine myself to the mere enumeration of the
phenomena of position, indicating, at the same time, some theoretic
views, by which observers in more advantageous circumstances than I
was myself may direct their researches.
12. AGGLOMERATE LIMESTONE OF THE BARIGON, OF THE CASTLE OF CUMANA, AND
OF THE VICINITY OF PORTO CABELLO.
This is a very complex formation, presenting that mixture and that
periodical return of compact limestone, quartzose sandstone and
conglomerates (limestone breccia) which in every zone peculiarly
characterises the tertiary strata. It forms the mountain of the castle
of San Antonio near the town of Cumana, the south-west extremity of
the peninsula of Araya, the Cerro Meapire, south of Caraco and the
vicinity of Porto Cabello. It contains (1) a compact limestone,
generally of a whitish grey, or yellowish white (Cerro del Barigon),
some very thin layers of which are entirely destitute of
petrifactions, while others are filled with cardites, ostracites,
pectens and vestiges of lithophyte polypi: (2) a breccia in which an
innumerable number of pelagic shells are found mixed with grains of
quartz agglutinated by a cement of carbonate of lime: (3) a calcareous
sandstone with very fine rounded grains of quartz (Punta Arenas, west
of the village of Maniquarez) and containing masses of brown iron ore:
(4) banks of marl and slaty clay, containing no spangles of mica, but
enclosing selenite and lamellar gypsum. These banks of clay appeared
to me constantly to form the lower strata. There also belongs to this
tertiary stratum the limestone tufa (fresh-water formation) of the
valleys of Aragua near Vittoria, and the fragmentary rock of Cabo
Blanco, westward of the port of La Guayra. I must not designate the
latter by the name of nagelfluhe, because that term indicates rounded
fragments, while the fragments of Cabo Blanco are generally angular,
and composed of gneiss, hyaline quartz and chloritic slate, joined by
a limestone cement. This cement contains magnetic sand,* (* This
magnetic sand no doubt owes its origin to chloritous slate, which, in
these latitudes, forms the bed of the sea.) madrepores, and vestiges
of bivalve sea shells. The different fragments of tertiary strata
which I found in the littoral Cordillera of Venezuela, on the two
slopes of the northern chain, seem to be superposed near Cumana
(between Bordones and Punta Delgada); in the Cerro of Meapire; on the
[Alpine] limestone of Cumanacoa; between Porto Cabello and the Rio
Guayguaza; as well as in the valleys of Aragua; on granite; on the
western declivity of the hill formed by Cabo Blanco, on gneiss; and in
the peninsula of Araya, on saliferous clay.
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