In this manner simultaneous temporary or permanent fissures are opened, by
which the interior of the Earth is brought in contact with the external
atmosphere. Molten masses, rising from an unknown depth, flow in narrow
streams along the declivity of mountains, rushing impetuously onward, or
moving slowly and gently, until the fiery source is quenched in the midst of
exhalations, and the lava becomes incrusted, as it were, by
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the solidification of its outer surface. New masses of rocks are thus
formed before our eyes, while the older ones are in their turn converted
into other forms by the greater or lesser agency of Platonic forces. Even
where no disruption takes place the crystalline moleculres are displaced,
combining to form bodies of denser texture. The water presents structures
of a totally different nature, as, for instance, concretions of animal and
vegetable remains, of earthy, calcareous, or aluminous precipitates,
agglomerations of finely-pulverized mineral bodies, covered with layers of
the silicious shields of infusoria, and with transported soils containing
the bones of fossil animal forms of a more ancient world. The study of the
strata which are so differently formed and arranged before our eyes, and of
all that has been so variously dislocated, conforted, and upheaved, by
mutual compression and volcanic force, leads the reflective observer, by
simple analogies, to draw a comparison between the present and an age that
has long passed.
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