Summing up these results, we find that the principal crops in Lower Egypt are cotton and rice. The cotton needs irrigation about once in twenty days, the rice once in ten days. To provide this amount of water, a canal should discharge (after allowance has been made for wastage) 22 cubic metres in twenty-four hours per acre of cotton, and 40 cubic metres per acre of rice. That is to say, 1 cubic metre per second will suffice for 4,000 acres of cotton and 2,150 acres of rice. In Upper Egypt rice is only a flood crop, and cotton and sugar need about 25 to 30 per cent. more water than in the Delta, owing to the greater loss from evaporation—that is to say, 1 cubic metre per second will only suffice for 3,000 acres of cotton or sugar. During the winter the land throughout Egypt requires on the average a watering once in forty days. But, as we have seen, it is the summer supply for the cotton that is the really important thing. We shall see later what the effect of the reservoir is likely to be in safeguarding and extending these interests. CHAPTER V THE DELTA BARRAGE AND THE ENGLISH ENGINEERS At the date of the English occupation the Delta Barrage was generally thought to be like the whole fabric of Egyptian Government, rotten to the core. And so indeed it seemed. No one had ever dared to use, or apparently even to think of using, the Barrage on the Damietta or right-hand branch at all. The history of the Barrage on the Rosetta branch was hardly less inglorious. In 1863 its gates were closed for the first time, but about ten of its arches began to settle, and ominous cracks showed. Eventually the threatened part was surrounded by a coffer-dam, and from 1872 to 1883 it managed to hold up about 1 metre. But even that was precarious. Commission after Commission had condemned the structure; it was felt that at any moment it might give way, especially if called upon to bear a greater strain, and it was actually the settled policy of the Government to rely on huge and costly pumping-stations instead. It was a paltry result after the expenditure of £4,000,000 and so much labour.