Up to the middle of July the Blue and White Niles keep increasing their discharges steadily at Khartoum, but after that date the Blue Nile gauge and discharge rise rapidly together, and the Blue Nile not only feeds the Main Nile, but flows up the White Nile and arrests its discharge, so that at Duem, 200 kilometres above Khartoum, the White Nile discharge decreases in July and August while the Blue Nile is steadily flowing up the White Nile valley and converting it into a reservoir for the Nile in winter. It is only after the 15th September, when the Blue Nile has begun to fall steadily and continuously that the White Nile discharge really commences and reaches its mean maximum of some 2000 cubic metres per second in October. The mean minimum discharge of the Nile of 650 cubic metres per second at Khartoum is obtained on the 1st May and the mean maximum of 9000 cubic metres per second on the 1st September. Fed by the White Nile reservoir the river falls comparatively slowly. Whether this peculiar relation of the two rivers to each other could not be taken advantage of to increase the supply in December, January and February, and decrease it in October and November by means of a regulating dam built across the White Nile at Khartoum is worthy of study. I greatly prefer the idea of storing the flood waters of the White Nile at Khartoum to any storage of the Albert Nile water above the junction of the Sobat river. A regulator above the Sobat junction would store up a very considerable quantity of water, but the quality would be very doubtful and possibly dangerous to health. At El Damer, south of Berber, the Atbara flows into the Nile. Dry from January to May, the flood begins in June and is at its maximum as a rule in the last week of August; with a mean high flood discharge of 3500 cubic metres per second. This water cannot come on to Assuân without filling up the 200 kilometres downstream of the 6th cataract where the slope of the Nile is gentle and the river lends itself to being used as a reservoir. It is owing to the fact that none of the main feeders of the Nile flow in immediately below cataracts that the rise and fall of the Nile in Egypt, is so regular and constant. If the Sobat, Blue Nile and Atbara all flowed into the White or Main Niles below cataracts we should have floods in Egypt whose sudden changes of level and fluctuations would be an unending source of danger to the country.