tirely to the last half century, cannot
possibly enable us to determine. But we know that strata, containing
species of shells identical with those now living in the contiguous
parts of the Mediterranean, have been raised in that country, as they
have in Sicily, to the height of several thousand feet.

Now, those geologists who grant that the present course of Nature in the
inanimate world has continued the same since the existing species of
animals were in being, will not feel surprised that the Calabrian
streams and rivers have cut out of such comparatively modern strata a
great system of valleys, varying in depth from fifty to six hundred
feet, and often several miles wide, if they consider how numerous may
have been the shocks which accompanied the uplifting of those recent
marine strata to so prodigious a height. Some speculators, indeed, who
disregard the analogy of existing nature, and who are always ready to
assume that her forces were more energetic in by-gone ages, may dispense
with a long series of movements, and suppose that Calabria "rose like an
exhalation" from the deep, after the manner of Milton's Pandemonium. But
such an hypothesis would deprive them of that peculiar removing force
required to form a regular system of deep and wide valleys; for _time_,
which they are so unwilling to assume, is essential to the operation.
Time must be allowed in the intervals between distinct convulsions, for
running water to clear away the ruins caused by landslips, otherwise the
fallen masses will serve as buttresses, and prevent the succeeding
earthquake from exerting its full power. The sides of the valley must be
again cut away by the stream, and made to form precipices and
over-hanging cliffs, before the next shock can take effect in the same
manner.

Possibly the direction of the succeeding shock may not coincide with
that of the valley, a great extent of adjacent country being equally
shaken. Still it will usually happen that no permanent geographical
change will be produced except in valleys. In them alone will occur
landslips from the boundary cliffs, and these will frequently divert the
stream from its accustomed course, causing the original ravine to become
both wider and more tortuous in its direction.

If a single convulsion of extreme violence should agitate at once an
entire hydrographical basin, or if the shocks should follow each other
too rapidly, the previously existing valleys would be annihilated