Their waters come charged with the debris 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.