owards one of the openings in the sea
bank, the city of Venice itself is built, on a crowded cluster of
islands; the various plots of higher ground which appear to the north
and south of this central cluster, have at different periods been also
thickly inhabited, and now bear, according to their size, the remains of
cities, villages, or isolated convents and churches, scattered among
spaces of open ground, partly waste and encumbered by ruins, partly
under cultivation for the supply of the metropolis.

Sec. VI. The average rise and fall of the tide is about three feet
(varying considerably with the seasons[3]); but this fall, on so flat a
shore, is enough to cause continual movement in the waters, and in the
main canals to produce a reflux which frequently runs like a mill stream.
At high water no land is visible for many miles to the north or south
of Venice, except in the form of small islands crowned with towers or
gleaming with villages: there is a channel, some three miles wide, between
the city and the mainland, and some mile and a half wide between it and
the sandy breakwater called the Lido, which divides the lagoon from the
Adriatic, but which is so low as hardly to disturb the impression of the
city's having been built in the midst of the ocean, although the secret of
its true position is partly, yet not painfully, betrayed by the clusters
of piles set to mark the deep-water channels, which undulate far away in
spotty chains like the studded backs of huge sea-snakes, and by the
quick glittering of the crisped and crowded waves that flicker and dance
before the strong winds upon the unlifted level of the shallow sea. But
the scene is widely different at low tide. A fall of eighteen or twenty
inches is enough to show ground over the greater part of the lagoon; and
at the complete ebb the city is seen standing in the midst of a dark
plain of seaweed, of gloomy green, except only where the larger branches
of the Brenta and its associated streams converge towards the port of
the Lido. Through this salt and sombre plain the gondola and the
fishing-boat advance by tortuous channels, seldom more than four or five
feet deep, and often so choked with slime that the heavier keels furrow
the bottom till their crossing tracks are seen through the clear sea
water like the ruts upon a wintry road, and the oar leaves blue gashes
upon the ground at every stroke, or is entangled among the thick weed
that fringes the banks with t