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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In Fact, There Are Immense Volcanoes In The Andes, Which
Have But Very Small Openings; And We Might Establish As
A
geological principle, that the most colossal mountains have craters
of little extent at the summits, if the Cordilleras did
Not present
many instances to the contrary.* (* The great volcanoes of Cotopaxi
and Rucupichincha have craters, the diameters of which, according
to my measurements, exceed 400 and 700 toises.) I shall have
occasion, in the progress of this work, to cite a number of facts,
which will throw some light on what may be called the external
structure of volcanoes. This structure is as varied as the volcanic
phenomena themselves; and in order to raise ourselves to geological
conceptions worthy of the greatness of nature, we must set aside
the idea that all volcanoes are formed after the model of Vesuvius,
Stromboli, and Etna.
The external edges of the Caldera are almost perpendicular. Their
appearance is somewhat like the Somma, seen from the Atrio dei
Cavalli. We descended to the bottom of the crater on a train of
broken lava, from the eastern breach of the enclosure. The heat was
perceptible only in a few crevices, which gave vent to aqueous
vapours with a peculiar buzzing noise. Some of these funnels or
crevices are on the outside of the enclosure, on the external brink
of the parapet that surrounds the crater. We plunged the
thermometer into them, and saw it rise rapidly to 68 and 75
degrees. It no doubt indicated a higher temperature, but we could
not observe the instrument till we had drawn it up, lest we should
burn our hands.
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