ay have been recently
introduced into the earth, to supply the places of plants and animals
which have from time to time disappeared. But granting that some such
secular variation in the zoological and botanical worlds is going on,
and is by no means wholly inappreciable to the naturalist, still it is
certainly far less manifest than the revolution always in progress in
the inorganic world. Every year some volcanic eruptions take place, and
a rude estimate might be made of the number of cubic feet of lava and
scoriae poured or cast out of various craters. The amount of mud and sand
deposited in deltas, and the advance of new land upon the sea, or the
annual retreat of wasting sea-cliffs, are changes the minimum amount of
which might be roughly estimated. The quantity of land raised above or
depressed below the level of the sea might also be computed, and the
change arising from such movements in a century might be conjectured.
Suppose the average rise of the land in some parts of Scandinavia to be
as much as five feet in a hundred years, the present sea-coast might be
uplifted 700 feet in fourteen thousand years; but we should have no
reason to anticipate, from any zoological data hitherto acquired, that
the molluscous fauna of the northern seas would in that lapse of years
undergo any sensible amount of variation. We discover sea-beaches in
Norway 700 feet high, in which the shells are identical with those now
inhabiting the German Ocean; for the rise of land in Scandinavia,
however insensible to the inhabitants, has evidently been rapid when
compared to the rate of contemporaneous change in the testaceous fauna
of the German Ocean. Were we to wait therefore until the mollusca shall
have undergone as much fluctuation as they underwent between the period
of the Lias and the Upper Oolite formations; or between the Oolite and
Chalk, nay, even between any two of eight subdivisions of the Eocene
series, what stupendous revolutions in physical geography ought we not
to expect, and how many mountain-chains might not be produced by the
repetition of shocks of moderate violence, or by movements not even
perceptible by man!

Or, if we turn from the mollusca to the vegetable kingdom, and ask the
botanist how many earthquakes and volcanic eruptions might be expected,
and how much the relative level of land and sea might be altered, or how
far the principal deltas will encroach upon the ocean, or the sea-cliffs
recede from the pres