The case would be quite altered were the sea to make new ways for itself, to attack the tongue of land and flow in and out wherever it chose. Not to mention that the little villages on the Lido, Pelestrina, viz., S. Peter's and others would be overwhelmed, the canals of communication would be choked up, and while the water involved all in ruin, the Lido would be changed into an island, and the islands which now lie behind it be converted into necks and tongues of land. To guard against this it was necessary to protect the Lido as far as possible, lest the furious element should capriciously attack and overthrow what man had already taken possession of, and with a certain end and purpose given shape and use to.
In extraordinary cases when the sea rises above measure, it is especially necessary to prevent it entering at more than two points. Accordingly the rest of the sluice-gates being shut, with all its violence it is unable to enter, and in a few hours submits to the law of the ebb, and its fury lessens.
Otherwise Venice has nothing to fear; the extreme slowness with which the sea-line retires, assures to her thousands of years yet, and by prudently deepening the canals from time to time, they will easily maintain their possessions against the inroads of the water.
I could only wish that they kept their streets a little cleaner--a duty which is as necessary as it is easy of performance, and which in fact becomes of great consequence in the course of centuries. Even now in the principal thoroughfares it is forbidden to throw anything into the canals: the sweepings even of the streets may not be cast into them. No measures, however, are taken to prevent the rain, which here falls in sudden and violent torrents, from carrying off the dirt which is collected in piles at the corner of every street, and washing it into the lagunes--nay, what is still worse, into the gutters for carrying off the water, which consequently are often so completely stopped up, that the principal squares are in danger of being under water. Even in the smaller piazza of S. Mark's, I have seen the gullies which are well laid down there, as well as in the greater square, choked up and full of water.