Page:Popular Science Monthly Volume 62.djvu/559

Rh are, of course, enormously increased. It will be recognized at once, therefore, that, as in the summer months the whole flow of the Nile is arrested and thrown into the aforesaid canals, the old barrage will always remain the most important work connected with the irrigation of Egypt. It was constructed under great difficulties by French engineers, subject to the passing whims of their Oriental chiefs. About fifteen years elapsed between the commencement of the work and the closing of all the sluices, and another twenty years before the structure was sufficiently strengthened by British engineers to fulfil the duties for which it was originally designed. All the difficulties arose from the nature of the foundations, as the timber sheet piling wholly failed to prevent the substructure from being undermined by the head of water carrying away the fine sand and silt upon which the barrage was built. At Asyût, cast-iron sheet piling was used, as will hereafter be described. It is impossible to say what the cost of the old barrage has been from first to last, but probably nearly ten times that of the recently-completed Asyût Barrage. Forced labor was largely employed in its construction, and at one time 12,000 soldiers, 3,000 marines, 2,000 laborers, and 1,000 masons were at work at the old barrage.

In connection with the Nile Reservoir, subsidiary weirs have been constructed below the old barrage to reduce the stress on that structure. The system adopted was a novel one, reflecting great credit on Major Brown, Inspector-General of Irrigation in Lower Egypt. His aim was to dispense almost entirely with plant and skilled labor; and so, without attempting to dry the bed of the river, he made solid masonry blocks under water, by grouting rubble dropped by natives into a movable timber caisson. Both branches of the Nile were thus dammed in three seasons, at a cost, including navigation locks, of about half a million sterling. Many other subsidiary works have been and will be constructed, including regulators, such as that on the Bahr Yusuf Canal.

By far the most important of the works constructed to enable the water stored up in the great reservoir to be utilized to the greatest advantage is the Barrage across the Nile at Asyût, about 250 miles above Cairo, which was commenced by Sir John Aird and Co. in the winter of 1898, and completed this spring. As already stated, in general principle this work resembles the old barrage at the apex of the Delta; but in details of construction there is no similarity, nor in material, as the old work is of brick and the new one of stone.

The total length of the structure is 2,750 feet, or rather more than half a mile, and it includes 111 arched openings of 16 feet 1 inches span, capable of being closed by steel sluice gates 16 feet in height. The object of the work is to improve the present perennial irrigation of lands in Middle Egypt and the Fayoum, and to bring an additional