Reefs and shoals, to the northeast of Lemnos, still indicate the spot where
the Aegean Sea once possessed an active volcano like Aetna, Vesuvius,
Stromboli, and Volcano (in the Lipari Isles).
Every stage of volcanic activity, from its first origin to its extinction,
is characterized by peculiar products; first by ignited scoriae, streams of
lava consisting of trachyte, pyroxene, and obsidian, and by rapilli and
tufaceous ashes, accompanied by the development
p 247
of large quantities of pure aqueous vapor; subsequently, when the volcano
becomes a solfatara, by aqueous vapors mixed with sulphureted hydrogen and
carbonic acid gases; and, finally, when it is completely cooled, by
exhalations of carbonic acid alone. There is a remarkable class of igneous
mountains which do not eject lava, but merely devastating streams of hot
water,* impregnated with burning sulphur and rocks reduced to a state of
dust (as, for instance, the Galungung in Java); but whether these mountains
present a normal condition, or only a certain transitory modification of the
volcanic process, must remain undecided until they are visited by geologists
possessed of a knowledge of chemistry in its present condition.
[footnote] *Compare Reinwardt and Hoffmann, in Poggendorf's 'Annalen', bd.
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