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the cross banks, and at the tail escapes into the river. In the more 
perfect basins the canals and escapes syphon under one another and 
overlap and supply each other’s deficiencies, so as to meet the require- 
ments of every kind of flood which Egypt can experience. Colonel 
Ross’s work on the basin irrigation of Egypt is a monument of patient 
observation and a storehouse of information. Some of the canals 
like the Sohagia on Plate XIY are veritable rivers, discharging 450 
cubic metres per second ; but a good average canal discharges 30 cubic 
metres per second. The largest canal has a width of 75 metres, while 
the average width is 9 metres. Good basin canals discharge in an 
average year one cubic metre per second per 700 acres. Forty-five 
days suffice for a perfect irrigation. The cost of providing basin irriga- 
tion in Egypt for basins of 10,000 acres may be taken at £3 per acre 
thus made up : — Banks, £1.50. ; canals, £*75. ; masonry works, £*50. ; 
and bank protection, £*25. If the basins are under 5,000 acres, the 
cost will be nearly double this. The annual cost of maintenance is £T0 
per acre ; while the lands themselves are rented at £3 per acre. In 
well irrigated basins no manures are needed, and alternate crops of cereals 
and legumins have been reaped for centuries without the land having 
been exhausted in any way whatever. Where the subsoil water is 
good and double cropping resorted to, then manures have to be applied. 
2 9 Perennial Irrigation. — The foundation-stone of the con- 
version of the whole of Egypt from basin to perennial irrigation was 
laid by Mehemet Ali in 1833, when he began the construction of the 
Barrages across the Nile branches north of Cairo. These weirs were 
intended to raise the summer level of the Nile by 3 metres. As the 
ordinary summer level of the Nile was 1.50 metres above its bed, the 
weirs were expected to raise it 4.50 metres above the Nile bed. The 
old basin canals had to be considerably deepened to take in the summer 
supplies ; while in other parts new perennial canals were dug. Peren- 
nial irrigation requires canals capable of discharging 1 cubic metre per 
second per 3500 acres, as against 700 acres for basin irrigation. Some 
of the perennial canals are very capacious. The two largest discharge 
700 and 450 cubic metres per second respectively. There are no 
artificial canals in the world like them. All the canals are liberally 
provided with regulators and locks. The energies of the Irrigation 
Department during the last ten years have been chiefly directed to the 
provision of sufficient drains to meet that over -saturation of the soil, 
which all but the best regulated perennial irrigation invariably entails. 
