Babylon, as we have already stated, stood upon the Euphrates, as Nineveh did upon the Tigris. A branch of it ran entirely through the city from north to south; and on each side was a quay, walled towards the river, of the same thickness as the city walls. In these, also, were gates of brass, from which persons descended to the water by steps; whence, for a long time, they crossed to the other side in boats; that is, until the building of a bridge. These gates were open always in the day, but shut at night. A bridge was at length erected; and this bridge was equally celebrated with the other great buildings; for it was of vast size; but Diodorus would seem to make it to have been much larger than it really was. He says it was five furlongs in length. Now as the Euphrates, at the spot, was only one furlong wide, this would be impossible; so we suppose that there must have been a causeway on each side of the bridge; and that Diodorus included the two causeways, which were, probably, merely dry arches, as we find in a multitude of modern bridges. It was, nevertheless, thirty feet in breadth, and built with great skill. The arches were of hewn stone, fastened together with chains of iron and melted lead. To effect the building with the greater care and safety, they turned the course of the river[99], and laid the channel dry. While one part of the workmen were doing this, others were shaping the materials for the quays, so that all were finished at the same time. During a certain portion of the year (viz., June, July, and August) the Euphrates overflows its banks, as the Nile does in Egypt, the Ganges in India, and the Amazon in South America. To remedy the manifold inconveniences arising from this, two large canals were cut to divert the superabundant waters into the Tigris, before they could reach Babylon[100]; and to secure the neighbouring country still the better, they raised artificial banks,--as the Dutch have done in Holland,--of a vast size, on both sides the river; not built, however, of earth, as in Holland, but of brick cemented with bitumen, which began at the head of the canals, and extended for some distance below the city. To effect all this, the Euphrates, which had been turned one way, in order to build the bridge, was turned another to build the banks. To this end they dug a vast lake, forty miles square, and one hundred and sixty in compass, and thirty-five feet deep. Into this lake the river was diverted, till the banks were finished; after which it was re-diverted into the former channel. The lake was, however, still preserved as a reservoir[101].