These few sentences
describe the general character of the products of volcanic activity.
p 234
Rocks which are merely broken through by the volcanic action are often
inclosed in the igneous products. Thus i have found angular fragments of
feldspathic syenite imbedded in the black augitic lava of the volcano of
Jorullo, in Mexico; but the masses of dolomite and granular limestone, which
contain magnificent clusters of crystalling fossils (vesuvian and garnets,
covered with mejonite, nepheline, and sodalite), are not the ejected
products of Vesuvius, these belonging rather to very generally distributed
formations, viz., strata of tufa, which are more ancient than the elevation
of the Somma and of Vesuvius, and are probably the products of a deep-seated
and concealed submarine volcanic action.*
[footnote] *Leop. von Buch, in Poggend., 'Annalen', bd. xxxvii., s. 179.
We find five metals among the products of existing volcanoes, iron, copper,
lead, arsenic, and selenium, discovered by Stromeyer in the crater of
Volcano.*
[footnote] *[The little island of Volcano is separated from Lipari by a
narrow channel. It appears to have exhibited strong signs of volcanic
activity long before the Christian era, and still emits gaseous exhalations.
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