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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Considering The Variety Of Structure Exhibited By Grottoes In Both
Hemispheres, We Cannot But Refer Their Formation To Causes Totally
Different.
When we speak of the origin of caverns we must choose
between two systems of natural philosophy:
One of these systems
attributes every thing to instantaneous and violent commotions (for
example, to the elastic force of vapours, and to the heavings
occasioned by volcanoes); while the other rests on the operation of
small powers, which produce effects almost insensibly by
progressive action. Those who love to indulge in geological
hypotheses must not, however, forget the horizontality so often
remarked amidst gypseous and calcareous mountains, in the position
of grottoes communicating with each other by passages. This almost
perfect horizontality, this gentle and uniform slope, appears to be
the result of a long abode of the waters, which enlarge by erosion
clefts already existing, and carry off the softer parts the more
easily, as clay or muriate of soda is found mixed with the gypsum
and fetid limestone. These effects are the same, whether the
caverns form one long and continued range, or several of these
ranges lie one over another, as happens almost exclusively in
gypseous mountains.
That which in shelly or Neptunean rocks is caused by the action of
the waters, appears sometimes to be in the volcanic rocks the
effect of gaseous emanations* acting in the direction where they
find the least resistance. (* At Vesuvius, the Duke de la Torre
showed me, in 1805, in currents of recent lava, cavities extending
in the direction of the current, six or seven feet long and three
feet high.
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