Boue's map of Europe, or to that
published by Mr. Lyell in the recent edition of his 'Principles of Geology'
(1847), from both of which it will become apparent that, at a comparatively
recent epoch, those parts of France, of Germany, of Hungary, and of Italy,
which afford evidences of volcanic action now extinct, were covered by the
ocean. Daubeney 'On Volcanoes', p. 605.] -- Tr.
In order to explain the necessity of the vicinity of the sea, recourse has
been had, even in modern times, to the hypothesis of the penetration of sea
water into the foci of volcanic agency, that is to say, into deep-seated
terrestrial strata. When I collect together all the facts that may be
derived from my own observation and the laborious researches of others, it
appears to me that every thing in this great quantity of aqueous vapors,
which are unquestionably exhaled from volcanoes even when in a state of
rest, be derived from sea water impregnated with salt, or rather, perhaps
with fresh meteoric water; or whether the expansive force of the vapors
(which, at a depth of nearly 94,000 feet, is equal to 2800 atmospheres)
would be able at different depths to counterbalance the hydrostatic pressure
of the sea, and thus afford them, under certain conditions, a free access to
the focus;* or whether the formation of metallic chlorids, the presence of
chlorid of sodium in the fissures of the crater, and the frequent mixture of
hydrochloric acid with the aqueous vapors, necessarily imply access of sea
water; or, finally, whether the repose of volcanoes (either when temporary,
or permanent and complete) depends upon the closure of the channels by which
the sea or meteoric water was conveyed, or whether the absence of flames and
of exhalations of hydrogen (and sulphureted hydrogen gas seems more
characteristic of solfataras than of active volcanoes) is not directly at
variance
p 245
with the hypothesis of the decomposition of great masses of water?**
[footnote] * Compare Gay-Lussac, 'Sur les Volcans', in the 'Annales de
Chimie', t.
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