297-309.
If hydrogen were evolved from erupted lava, how great must be the quantity
of the gas disengaged, when, the seat of the volcanic activity being very
low, as in the case of the remarkable eruption at the foot of the Skaptar
Jokul in Iceland (from the 11th of June to the 3d of August, 1783, described
by Mackenzie and Soemund Magnussen), a space of many square miles was
covered by streams of lava, accumulated to the thickness of several hundred
feet! Similar difficulties are opposed to the assumption of the penetration
of the atmospheric air into the crater, or, as it is figuratively expressed,
the 'inhalation of the earth', when we have regard to the small quantity of
nitrogen emitted. So general, deep-seated, and far-propagated an activity
as that of volcanoes, can not assuredly have its source in chemical
affinity, or in the mere contact of individual or merely locally distributed
substances. Modern geognosy* rather seeks the cause of this activity in the
increased temperature with the increase of depth at all degrees of latitude,
in that powerful internal heat which our planet owes to its first
solidification, its formation in the regions of space, and to the spherical
contraction of
p 237
matter revolving elliptically in a gaseous condition.
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