The advance
p 213
from south to north was very striking in the almost uninterrupted
undulations of the soil in the alluvial valleys of the Mississippi, the
Arkansas, and the Ohio, from 1811 to 1813. It seemed here as if
subterranean obstacles were gradually overcome, and that the way being once
opened, the undulatory movement could be freely propagated.
Although earthquakes appear at first sight to be simply dynamic phenomena of
motion, we yet discover, from well-attested facts, that they are not only
able to elevate a whole district above its ancient level (as for instance,
the Ulla Bund, Delta of the Indus, or the coast of Chili, in November,
1822), but we also find that various substances have been ejected during the
earthquake, as hot water at Catania in 1818; hot steam at New Madrid, in the
Valley of the Mississippi, in 1812; irrespirable gases, 'Mofettes', which
injured the flocks grazing in the chain of the Andes; mud, black smoke, and
even flames, at Messina in 1781, and at Cumana on the 14th of November,
1797. During the great earthquake of Lisbon, on the 1st of November, 1755,
flames and columns of smoke were seen to rise from a newly-formed fissure in
the rock of Alvidras, near the city. The smoke in this case became more
dense as the subterranean noise increased in intensity.
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