18 COTTON IN EGYPT AND THE SUDAN. 



usual height have caused the devastation of the fruitful lands. In 

 this way the Nileometer is the national clock for the well-being of 

 Egypt, and its movements are even to-day watched with anxiety just 

 as in the olden days, although owing to the extensive canal system 

 such damage is to-day impossible. 



In order to prevent that the high waters of the Nile pour their 

 fruitful contents too fast into the sea, the whole of the culturable 

 land has been divided since ancient times into large basins (Hods) 

 by means of dams which, during the flood-time, serve as a line of 

 communication. These basins, holding 500 to 48,000 hectares, are 

 formed by a dam running parallel to the main stream, which pre- 

 vents the direct flooding of the latter, and by two dams at right 

 angles to the first dam, with an inlet and an outlet canal which 

 have sluices built partly of brick. At the time of the flood these 

 basins, which run from north to south, step-like, falling from north 

 to south, are filled under the superintendence of special engineers, 

 and the valuable water is held for a certain time usually from six 

 to seven weeks in one of these basins until the proper amount of 

 silt has been deposited, i.e., a deposit of about 15,0001bs. of solid 

 substance per feddan. The water either flows then straight into the 

 Nile or it is taken to a lower-lying field, although it has by then 

 become impoverished. The water supply thus accumulated had to 

 suffice for the cultivation. 



Up to the year 1837 this basin irrigation by flooding was the 

 only way of irrigating independently from the direct flood of the 

 Nile. As cotton cultivation is carried on in summer, and cannot be 

 undertaken in the fields watered by means of this basin irrigation, 

 Mohammed All introduced an irrigation system into the Delta, in 

 which the basins were replaced by a network of canals which were 

 filled at the time of the flood of the Nile, and through this system 

 the water was held back in the main canals, whilst the tributary 

 canals were only periodically filled with water; special drainage 

 canals carried the water off into the sea which was no longer 

 required. The building of the first bridge-dam or weir in the Delta 

 was also undertaken by Mohammed Ali, and carried out with the 

 aid of French engineers, although not in a satisfactory manner. 



After these great improvements there came a long lull, and it was 

 only after the occupation of Egypt by the English that with the prac- 

 tice gained in India the working-out on a larger scale of the irriga- 

 tion system was begun. In order to make cultivation less dependent 

 upon the different heights of the Nile floods, it was then decided to 

 store up the ample water supply of the Nile and to use it for cultiva- 

 tion, chiefly for cotton, by means of so-called "perennial canals," 

 from which at any time of the year water could be had in any desired 

 quantities. 



As the masterpiece of the great weirs that have been constructed 

 by the English must be considered the Assuan Dam, that has been 

 built between 1898 and 1902, according to the plans of the engineers 

 Scott-Moncrieff, Garstin, & Willcocks ; it is nearly 2 kilometres long, 

 and its basins hold the water back during November, December, and 

 January, to be used for cultivation in summer, i.e., up to the beginning 

 of July. As long as the flood-water of the Nile is very muddy all 

 the 180 sluice gates of the dam are kept open ; in October and 



