[footnote] *[True volcanoes, as we have seen, generate sulphureted hydrogen
and muriatic acid, upheave tracts of land, and omit streams of melted
feldspathic materials; salses, on the contrary, disengage little else but
carbureted hydrogen, together with bitumen and other products of the
distillation of coal, and pour forth no other torrents except of mud, or
argillaceous materials mixed up with water. Daubeney, op cit., p. 540.] --
Tr.
If we consider these mountains as springs of molten earths producing
volcanic rocks, we must remember that thermal water, when impregnated with
carbonic acid and sulphurous gases, are continually forming horizontally
ranged strata of limestone (travertine) or conical elevations, as in
Northern Africa (in Alberia), and in the Banos of Caxamarca, on the western
declivity of the Peruvian Cordilleras. The travertine of Van Diemen's Land
(near Hobart Town) contains, according to Charles Darwin, remains of a
vegetation that no longer exists. Lava and travertine, which are constantly
forming before our eyes, present us with the two extremes of geognostic
relations.
'Salses' deserve more attention than they have hitherto received from
geognosists. Their grandeur has been overlooked because of the two
conditions to which they are subject; it is only the more peaceful state, in
which they may continue for centuries, which has generally been described:
their origin is, however, accompanied by earthquakes, subterranean thunder,
the elevation of a whole district, and lofty emissions of flame of short
duration.
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