SECTION III. When the eye falls casually on a map of Europe, there is no
feature by which it is more likely to be arrested than the strange
sweeping loop formed by the junction of the Alps and the Apennines, and
enclosing the great basin of Lombardy. This return of the mountain chain
upon itself causes a vast difference in the character of the
distribution of its debris on its opposite sides. The rock fragments and
sediment which the torrents on the north 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.

SECTION IV. 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