The rock fragments and sediment which the
torrents on the other side of the Alps bear into the plains are
distributed over a vast extent of country, and, though here and there
lodged in beds of enormous thickness, soon permit the firm substrata to
appear from underneath them; but all the torrents which descend from
the southern side of the High Alps, and from the northern slope of the
Apennines, meet concentrically in the recess or mountain bay which the
two ridges enclose; every fragment which thunder breaks out of their
battlements, and every grain of dust which the summer rain washes from
their pastures, is at last laid at rest in the blue sweep of the
Lombardic plain; and that plain must have risen within its rocky
barriers as a cup fills with wine, but for two contrary influences
which continually depress, or disperse from its surface, the
accumulation of the ruins of ages.
I will not tax the reader's faith in modern science by insisting on the
singular depression of the surface of Lombardy, which appears for many
centuries to have taken place steadily and continually; the main fact
with which we have to do is the gradual transport, by the Po and its
great collateral rivers, of vast masses of the finer sediment to the
sea. The character of the Lombardic plains is most strikingly expressed
by the ancient walls of its cities, composed for the most part of large
rounded Alpine pebbles alternating with narrow courses of brick; and
was curiously illustrated in 1848, by the ramparts of these same
pebbles thrown up four or five feet high round every field, to check
the Austrian cavalry in the battle under the walls of Verona.
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