— 60 — 
Through October the Nile at Cairo is practically stationary, and falls 
rapidly in November. 
North of Cairo are the heads of the perennial canals which irrigate 
the Delta proper. The canals, with their feeders lower down, discharge 
1,200 cubic metres per second, and the ordinary maximum flood at 
Cairo of 7,600 cubic metres per second is reduced by this amount 
between Cairo and the sea. Of the 6,400 cubic metres per second which 
remain, 4,100 cubic metres per second find their way to the sea down 
the Rosetta branch, and 2,300 cubic metres per second down the 
Damietta branch. During extraordinary floods the Damietta branch 
has discharged 4,300 cubic metres per second and the Rosetta branch 
7,000 cubic metres per second. 
25. The Nile in low supply.— We have so far considered the 
Nile in flood, it now remains to quickly dispose of the low supply. 
After reaching its maximum, the Atbara, which is a torrential river, 
falls more rapidly than others, and by the end of September has practi- 
cally disappeared ; after the middle of September the Blue Nile falls 
quickly, while the White Nile with its large basin, gentle flow and 
numerous reservoirs, falls very deliberately. The mean minimum 
discharge of the White Nile at Gondokoro in an ordinary year, at the 
time of low supply, is 600 cubic metres per second. Of the Sobat 
river it is 100 cubic metres per second. By the time the water reaches 
Khartoum it is reduced to 450 cubic metres per second. The mean low 
supply of the Blue Nile is 200 cubic metres per second, giving a mean 
low supply to the Nile at Khartoum of 650 cubic metres per second. 
The Atbara supplies nothing. Between Khartoum and Assuan there 
is a further loss of 60 cubic metres per second, and the mean low supply 
delivered at Assuan is 590 cubic metres per second. In very bad years 
the discharge at Assuan has fallen to 400 cubic metres per second. 
Lombardini was no untrue prophet when he wrote that he was 
convinced that the more carefully the discharges were taken and the 
results known, the more would engineers be astonished at the extra- 
ordinary amount of the subsoil water which filtered into the Nile 
from the head of the White Nile to the sea, and which gave back to 
the Nile in the months of deflux of the river, the water which had 
percolated into the soil during the afflux. He predicted that heavy as 
the evaporation was in April, May and June in the Nile valley, the 
influx of subsoil water would be found to counterbalance it. When 
we calculate the extent of the water used in irrigation along the 
