After having spoken of the alteration of compact carbonate of lime into
granular limestone and dolomite, it still remains for us to mention a third
mode of transformation of the same mineral, which is ascribed to the
emission, in the ancient periods of the world, of the vapors of sulphuric
acid. This transformation of limestone into gypsum is analogous to the
penetration of rock salt and sulphur, the latter being deposited from
sulphureted aqueous vapor. In the lofty Cordilleras of Quindin, far from
all volcanoes, I have observed deposits of sulphur in fissures in gneiss,
while in Sicily (at Cattolica, near Girgenti), sulphur, gypsum, and rock
salt belong to the most recent secondary strata, the chalk formations.*
[footnote] *Horrman, 'Geogn. Reise', edited by Von Dechen, s. 113-119, and
380-386; Poggend., 'Annalen der Physik', bd. xxvi., s. 41.
I have also seen on the edge of the crater of Vesuvius, fissures filled with
rock salt, which occurred in such considerable masses as occasionally to
lead to its being disposed of by contraband trade. On both declivities of
the Pyrenees, the connection of diorite and pyroxene, and colomite, gypsum,
and rock salt, can not be questioned;* and here, as in the other phenomena
which we have been considering, every thing bears evidence of the action of
subterranean forces on the sedimentary strata of the ancient sea.
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