From these reservoirs the water is conducted by pipes, formed of cylindrical tiles jointed together, and so conveyed to the city a distance of about fifteen miles. The ravines, that break the intervening country, are crossed by aqueducts, some of vast dimensions, striding the valleys, and towering above the forests. They are whitewashed at stated intervals, and form striking objects in distant prospects, strongly relieved by the dark woods above which they rise. One of them terminates the view up the great valley of Buyukderé, and seems, to mariners passing on the Bosphorus, like the battlements of a large city, on the distant horizon. Besides these, there are others of more peculiar structure. They are insulated hydraulic pillars, called _Souterrais_, standing in long rows, like slender square castles or watch-towers. The water ascends one side of each, is received into a small square reservoir on the summit, and from thence descends the other. It climbs the next in a similar manner; and by this contrivance, for which the Turks are indebted to the Arabs, the vast expense of aqueducts is saved, and the water conveyed by many channels over various hills and valleys, in continued and never-ceasing streams, to its magnificent reservoirs in the city. When the water arrived here, it had the same irregularity of surface to oppose, its seven hills to surmount, and seven valleys between them to cross. This was effected by a second series of aqueducts, which are described by the Byzantine historians with all the inflated language of astonishment. They are represented as “subterranean rivers” conducted through the air over the city, while the people gaze in wonder from below. Of these, but one remains to attest what they were. This is the aqueduct of Valens, stretching from hill to hill, and seen in almost every direction. Its erection was the completion of a singular prophecy: On the ramparts of Chalcedon was found a stone with an occult inscription, implying that “the walls of the city should bring water to Constantinople.” To extend these walls across the sea, seemed altogether an impossibility, and the oracular announcement was despised. But Chalcedon having incurred the resentment of the emperor, its walls were pulled down, the stones conveyed to Constantinople for building, and, among other erections formed of them, was the aqueduct of Valens, thereby accomplishing the oracle.