when the river is low, in the shape of a very broad sheet of shingle studded thick with fresh-water oysters. This bar is 6 kilometres long, as hard as stone, and has in very low summer supplies a depth of water over it of only 50 centimetres. It is a wonder that a channel has not been blasted through it. The swamping now visibly decreases and the width of the river varies from 700 to 900 metres. Some 25 kilometres north of Abu Zeid the papyrus and sudd grasses disappear, and though there is flooding there are no swamps. We have now some well cultivated islands in the river for the negroes have come to an end and the Arabs inhabit the country. The summer channel may be now considered as 700 metres wide and the flood channel as 1300 metres. The summer depth of water is 4 metres. At Duem, 220 kilometres south of Khartoum, the width of the channel widens from 900 to 1000 and further north to 1500 metres, and finally to 3000 metres. We are in a lake rather than in a river, and in flood when the waters of the Blue Nile travel 300 kilometres up the White Nile, and wait for a fall in the Blue Nile to discharge themselves into the Nile, we are indeed in a pulsating lake and not in a river. It must have been in September, when the discharge of the Blue Nile had fallen from some 11,000 to 6,000 cubic metres per second, and the stored-up waters in the valley of the White Nile were forcing themselves down to take the place of those cut off from the Blue Nile, that Linant Pasha took his discharges of the Blue and White Niles and found them some 6000 and 5000 cubic metres per second respectively. The same remark may be made about M. Chélu’s discharge of the White Nile at Khartoum of 4000 cubic metres per second in September 1876 and mentioned in his book “_Le Nil, le Soudan, l’Égypte_,” page 17. [Illustration: PLATE IX. CROSS SECTIONS OF THE NILE & ITS TRIBUTARIES _Horizontal Scale 1 : 2.000_ _Vertical Scale 1 : 500_ Lith. Sur. Dep. Cairo. No. 14. _White Nile at Duem._ No. 15. _Blue Nile at Lake Tsana_ No. 16. _Blue Nile at the Bridge 30 km. from Lake Tsana_ No. 17. _Blue Nile at Wad Medani_ No. 18. _Blue Nile at Khartoum_]