The recent danger, to which the person of the emperor had been exposed in the defenceless palace of Milan, urged him to seek a retreat in some inaccessible fortress of Italy, where he might securely remain, while the open country was covered by a deluge of Barbarians. On the coast of the Adriatic, about ten or twelve miles from the most southern of the seven mouths of the Po, the Thessalians had founded the ancient colony of Ravenna, which they afterwards resigned to the natives of Umbria. Augustus, who had observed the opportunity of the place, prepared, at the distance of three miles from the old town, a capacious harbor, for the reception of two hundred and fifty ships of war. This naval establishment, which included the arsenals and magazines, the barracks of the troops, and the houses of the artificers, derived its origin and name from the permanent station of the Roman fleet; the intermediate space was soon filled with buildings and inhabitants, and the three extensive and populous quarters of Ravenna gradually contributed to form one of the most important cities of Italy. The principal canal of Augustus poured a copious stream of the waters of the Po through the midst of the city, to the entrance of the harbor; the same waters were introduced into the profound ditches that encompassed the walls; they were distributed by a thousand subordinate canals, into every part of the city, which they divided into a variety of small islands; the communication was maintained only by the use of boats and bridges; and the houses of Ravenna, whose appearance may be compared to that of Venice, were raised on the foundation of wooden piles. The adjacent country, to the distance of many miles, was a deep and impassable morass; and the artificial causeway, which connected Ravenna with the continent, might be easily guarded or destroyed, on the approach of a hostile army. These morasses were interspersed, however, with vineyards: and though the soil was exhausted by four or five crops, the town enjoyed a more plentiful supply of wine than of fresh water. The air, instead of receiving the sickly, and almost pestilential, exhalations of low and marshy grounds, was distinguished, like the neighborhood of Alexandria, as uncommonly pure and salubrious; and this singular advantage was ascribed to the regular tides of the Adriatic, which swept the canals, interrupted the unwholesome stagnation of the waters, and floated, every day, the vessels of the adjacent country into the heart of Ravenna. The gradual retreat of the sea has left the modern city at the distance of four miles from the Adriatic; and as early as the fifth or sixth century of the Christian æra, the port of Augustus was converted into pleasant orchards; and a lonely grove of pines covered the ground where the Roman fleet once rode at anchor. Even this alteration contributed to increase the natural strength of the place, and the shallowness of the water was a sufficient barrier against the