The city of Venice stands on a cluster of low sandy islands. It is
probable that the country which lies nearest to the gulf, if not the
whole of the immense plain of Lombardy itself, is of alluvial formation.
Whatever may have been the origin of that wide and fertile kingdom, the
causes which have given to the Lagunes their existence, and to Venice
its unique and picturesque foundation, are too apparent to be mistaken.
Several torrents which flow from the valleys of the Alps pour their
tribute into the Adriatic at this point. Their waters come charged with
the débris of the mountains, pulverized nearly to their original
elements. Released from the violence of the stream, these particles have
necessarily been deposited in the gulf, at the spot where they have
first become subjected to the power of the sea. Under the influence of
counteracting currents, eddies, and waves, the sands have been thrown
into submarine piles, until some of the banks have arisen above the
surface, forming islands, whose elevation has been gradually augmented
by the decay of vegetation. A glance at the map will show that, while
the Gulf of Venice is not literally, it is practically, considered with
reference to the effect produced by the south-east wind called the
Sirocco, at the head of the Adriatic. This accidental circumstance is
probably the reason why the Lagunes have a more determined character at
the mouths of the minor streams that empty themselves here than at the
mouths of most of the other rivers, which equally flow from the Alps or
the Apennines into the same shallow sea.

The natural consequence of a current of a river meeting the waters of
any broad basin, and where there is no base of rock, is the formation,
at or near the spot where the opposing actions are neutralized, of a
bank, which is technically called a bar. The coast of the Union
furnishes constant evidence of the truth of this theory, every river
having its bar, with channels that are often shifted, or cleared, by the