The barrage is a double bridge, or weir, the eastern part spanning the Damietta branch of the Nile, the western part the Rosetta branch. The appearance of the structure is so light and graceful that the spectator finds it hard to conceive of the difficulty and the greatness of the work itself. Architecturally, the barrage is very beautiful, with a noble front and a grand effect, produced by a line of castellated turrets, which mark the site of the sluice gates. There are two lofty crenellated towers, corresponding with the towers over the gateway of a mediaeval baronial castle. The sluices are formed of double cones of hollow iron, in a semicircular form, worked on a radii of rods fixed to a central axis at each side of the sluice-gate. They are slowly raised or let down by the labour of two men, the gates being inflected as they descend in the direction of the bed of that part of the river whose waters are retained. The working of the barrage was never what it was intended to be. After the year 1867 it ceased to be of any practical utility, and was merely an impediment to navigation. Between the years 1885--90, however, during the British occupation, Sir Colon Scott-Moncrieff successfully completed the barrage at a cost of $2,500,000, and now the desired depth of eight feet of water on the lower part of the Nile can always be maintained. [Illustration: 241.jpg THE NILE BARRAGE] It proved to be of the greatest advantage in saving labour worth hundreds of thousands of dollars a year, and in the irrigation and navigation facilities that had been contemplated as among the benefits which would naturally accrue from its successful completion. Compared with the advance of the land seaward at the estuary of the Mississippi and the Ganges, the advance of the Nile seaward is very slow. This is accounted for by the geological theory that the Delta of the Nile is gradually sinking. If this is so, the tendency of the periodical deposit to raise the level of the Delta will be counteracted by the annual subsidence. These phenomena account for the gradual burial of Egyptian monuments under the sand, although the actual level of the sea above what it formerly was is quite unappreciable.