Observe, first, you have the
whole mass of the rock in motion, either contracting itself, and
so gradually widening the cracks, or being compressed, and thereby
closing them, and crushing their edges,--and, if one part of its
substance be softer, at the given temperature, than another,
probably squeezing that softer substance out into the veins. Then
the veins themselves, when the rock leaves them open by its
contraction, act with various power of suction upon its
substance;--by capillary attraction when they are fine,--by that
of pure vacuity when they are larger, or by changes in the
constitution and condensation of the mixed gases with which they
have been originally filled. Those gases themselves may be
supplied in all variation of volume and power from below; or,
slowly, by the decomposition of the rocks themselves; and, at
changing temperatures, must exert relatively changing forces of
decomposition and combination on the walls of the veins they fill;
while water, at every degree of heat and pressure (from beds of
everlasting ice, alternate with cliffs of native rock, to volumes
of red hot, or white hot, steam), congeals, and drips, and throbs,
and thrills, from crag to crag; and breathes from pulse to pulse
of foaming or fiery arteries, whose beating is felt through chains
of the great islands of the Indian seas, as your own pulses lift
your bracelets, and makes whole kingdoms of the world quiver in
deadly earthquake, as if they were light as aspen leaves.
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