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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Gneiss-Granite And
Mica-Slate Constitute The Summits Of The Ridge, In The Almost
Insulated Group Of The Sierra Nevada
Of Grenada and the Peak of
Malhacen,* (* This peak, according to the survey of M. Clemente Roxas,
is 1826 toises
Above the level of the sea, consequently 39 toises
higher than the loftiest summit of the Pyrenees (the granitic peak of
Nethou) and 83 toises lower than the trachytic peak of Teneriffe. The
Sierra Nevada of Grenada forms a system of mountains of mica-slate,
passing to gneiss and clay-slate, and containing shelves of euphotide
and greenstone.), as they also do in the continuous chain of the Alps,
the Pyrenees and probably the Himalayas.* (* If we may judge from the
specimens of rocks collected in the gorges and passes of the Himalayas
or rolled down by the torrents.) These phenomena, discordant in
appearance, are possibly all effects of the same cause: granite,
gneiss, and all the so-styled primitive Neptunian mountains, may
possibly owe their origin to volcanic forces, as well as the
trachytes; but to forces of which the action resembles less the
still-burning volcanoes of our days, ejecting lava, which at the
moment of its eruption comes immediately into contact with the
atmospheric air; but it is not here my purpose to discuss this great
theoretic question.
After having examined the general structure of South America according
to considerations of comparative geology, I shall proceed to notice
separately the different systems of mountains and plains, the mutual
connection of which has so powerful an influence on the state of
industry and commerce in the nations of the New Continent.
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