Les laves qui n'ont pas ete
submergees, n'en contiennent jamais. J'ai trouve ces observations si
constantes, que par-tout ou je rencontrois de la zeolite, j'etois sur
de trouver d'autres preuves de submersion, et partout ou je voyois des
laves recouvertes des depots de l'eau, j'etois sur de trouver de la
zeolite, et un de ces faits m'a toujours indique l'autre. Je me suis
servi avec succes de cette observation pour diriger mes recherches, et
pour connoitre l'antiquite des laves. _Mineralogie de Volcans, par
M. Faujas de Saint-Fond_. Here would appear to be the distinction of
subterraneous lava, in which zeolite and calcareous spar may be found,
and that which has flowed from a volcano, in which neither of these are
ever observed.]
There can be no doubt that these two different species of bodies have
had the same origin, and that they are composed of the same materials
nearly; but from the different circumstances Of their production, there
is formed a character to these bodies, by which, they may be perfectly
distinguished. The difference of those circumstances consists in this;
the one has been emitted to the atmosphere in its fluid state the other
only came to be exposed to the light in a long course of time, after it
had congealed under the compression of an immense load of earth, and
after certain operations, proper to the mineral regions, had been
exercised upon the indurated mass.
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