ASSOUAN, 4-swan', or ASSUAN, also called Aswan (Arabic al suaan, °the opening," that is, of the Nile; the ancient Syene, whence the red granite of the vicinity— from whose famous quarries were cut under the earliest dynasties so many of the huge obelisks and colossal statues that adorned the temples and palaces of Egypt—is called syenite), capital of the province of the same name, the south ernmost city of Egypt proper, near Nubia, on the right or eastern bank of the Nile, and beside the first or lowest cataract, 590 miles by rail south of Cairo. Near it are the islands of Philm and Elephantine, the ruined monu ments of the former of which are of such fascination to tourists; on the left bank are many rock tombs of the ancient dynasties. Up to the crushing of the Mandist rebellion Assouan was an important garrison town and the central depot for the Sudan caravan trade. This, as well as its military importance, has since declined but the opening of a railway to Alexandria has increased its commercial pros perity. The chief export is senna. Assouan is also a famous health and tourist resort.
• Pop. (1907),. including suburbs, 16,125. Of still greater importance is the new dam which has added 1,408,000 acres to the arable soil of Egypt, besides steadying the fertility of the older lands, and which is described in extenso below.
The monumental dam at Assouan, one of the greatest achievements of the kind in ancient or modern times, forms a reservoir in the Nile Valley capable of storing 2,423,000.000 cubic metres of water. It has not only pro duced a revolution in tile primitive and labori ous methods of irrigation in Egypt, but has reclaimed vast areas of land that have hitherto been accounted as arid and worthless. The old system of irrigation was little more than a high Nile flooding of different areas of land or basins surrounded by embankments. Less than a hundred years ago the introduction of perennial irrigation was first attempted under Inchemet Ali by cutting deep canals to convey the water to the lands when the Nile was at its low summer level. When the Nile rose, these canals had to be blocked by temporary earthen dams, or the current would have wrought de struction. As a result, they silted up, and had to be cleared of many millions of tons of mud each year by enforced labor, much misery and extortion resulting therefrom. About half a century ago the first serious attempt to im prove matters was made by the construction of the celebrated Barrage at the apex of the delta. This work consists, in effect, of two brick-arched viaducts crossing the Rosetta and Damietta, branches of the Nile, having together 132 arches of 16 feet 4 inches span, which were entirely closed by iron sluices during the summer months, thus heading up the water some 15 feet and throwing it at a high level into the six main irrigation canals below Cairo. In the summer months the whole flow of the Nile is arrested and thrown into the aforesaid canals. The old Barrage was constructed under great difficulties by French engineers, subject to the passing whims of their Oriental chiefs. About 15 years elapsed between the commencement of the work and the closing of all the sluices, and another 20 years before the structure was sufficiently strengthened by British engineers to fulfil the duties for which it was originally designed. Forced labor was largely employed in its con struction 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 sub sidiary weirs were constructed below the old Barrage to reduce the stress on that structure. The system adopted was a novel one, devised by Major Brown, inspector-general of irriga tion 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 sea sons at a cost, including navigation locks, of about $2,500,000. Many other subsidiary works have been and will he constructed, including regulators such as that on the Bahr Yusuf Canal. The most important of the works are the Barrage across the Nile at Assiut, about 250 miles above Cairo, which was commenced by Sir John Aird & Co. in the winter of 1898 and completed in 1902, the Barrage at Zifta, designed and built by Sir Hanbury Brown, 1900-02; and the Barrage at Esna, designed by Sir Arthur Webb, built by M. McDonald, 1906-08. The great dam at Assouan, 590 miles above Cairo, is not a solid wall, but is pierced with sluice openings of sufficient area for the flood discharge of the river, which may amount to 15,000 tons of water per sec ond. There are 180 such openings, the lower 140 are 23 feet high by feet wide, the up per 40 are 11 by feet; and where subject to heavy pressure when being moved they are of the well-known Stoney rollerpattern. The total length of the dam is about miles; the original height from foundation, about 130 feet; the difference of level water above and below, 65 feet; and the weight of masonry 149.5 pounds per cubic foot. The total ex cavation has been estimated at 824,000 cubic yards and the masonry at 704,000 cubic yards. Navigation is provided for by a °ladder° of four locks, each 260 feet long by 32 feet wide. As was the case at Assiut, the difficulties in dam construction are not in design but in the carrying out of the works. When the °rotten rock° in the bed was discovered, Sir Benjamin Baker reported to Lord Cromer frankly that he could not say what the extra cost or time involved by this and other unforeseen condi tions would be, and that all that could be said was that, however •bad the conditions, the job could be done. Lord Cromer replied that the dam had to be completed whatever the time and cost involved. The contract was let to Sir John Aird & Co., of London, with Messrs. Ransomes and Rapier, of London, as sub-contractors for the iron work, in Febru ary 1898. The engineer who designed it was Sir William Willcocks. Two months after signing the contract the permanent works were commenced, and before the end of the year thousands of native laborers and hundreds of Italian granite masons were hard at work. On 12 Feb. 1899, the foundation stone of the dam was laid by the Duke of Connaught. Many plans were considered by the engineers and contractors for putting in the foundations of the dam across the roaring cataract chan nels, and it was finally decided to form tem porary rubble dams across three of the chan nels below the site of the great dam, so as to break the force of the torrent and get a pond of comparatively still water up stream to work in. Stones of from one ton to 12 tons in weight were tipped into the cataract, till finally a rubble mound appeared above the surface. The first channel was successfully closed on 17 May 1899, the depth being about 30 feet and the velocity of current nearly 15 miles an hour. In the case of another channel the clos ing had to be helped by tipping in railway cars themselves, loaded with heavy stones and bound together with wire ropes, a mass of about 50 tons, the great mass being necessary to resist displacement by the torrent.