_Vertical Scale 1 : 500_ Lith. Sur. Dep. Cairo. No. 19. _River Rahad at Khor Abou Seghire 20 km. above the Nile junction_ No. 20. _Atbara River at Khashim al Girba 410 km. from Nile_ No. 21. _Atbara River at Khor Abadar 25 km. from Nile_ No. 22. _Nile at Manfalout_ No. 23. _Rosetta Branch at Khatatba_ No. 24. _Damietta Branch at Benha_] Tables 41 to 52 refer to the Nile between Assuân and the Barrage at the head of the Delta proper. Table 46 gives the Reduced Level of the mean low water level of the Nile at various points between Assuân and Cairo. If, for example, it is known that the water surface at any time of the year at Assiout is R. L. 50.80, we know the mean low water by the Irrigation Department levels is 45.05. The gauge is therefore 5.75, and by turning to Table 37 we know the discharge. Table 37 gives the discharges of the river for gauges referred to the mean low water level. Between Esna and Kena the table is in excess of the truth, and between Assiout and Beni-Suef it is slightly under. Taken all round the table is reliable, calculated from the means of hundreds of discharges and carefully prepared. Table 45 gives the slope of the water surface of the Nile in flood and in summer between Assuân and Cairo. Owing to the more winding track of the low supply than of the flood waters, the former is 948 kilometres and the flood 900. The slope in summer is ¹⁄₁₃₀₀₀ and in high flood ¹⁄₁₂₂₀₀. The other tables need no explanation. 23. =The Rosetta and Damietta Branches.=--Plates XVII and XVIII give longitudinal sections of the two branches of the Nile and their cross sections are given on Plate XI. During winter, summer, and low floods, regulation at the Barrage interferes with the natural discharges of the two branches. The Damietta branch is gradually silting up and decreasing in size, while the Rosetta branch scours in high floods. The mean width of the Rosetta branch is 500 metres, and the mean area of the section in flood is 4000 square metres. The mean width of the Damietta branch is 270 metres and the mean section 2700 square metres. The mean velocity of the floods range from 1.00 metre to 1.60 metres per second. In summer the branches are hermetically closed at their heads and receive only the water which filters into them from the subsoil. This in the Rosetta branch amounts to 20 cubic metres per second, and less in the Damietta branch. It may be noted here that at Cairo the girder bridge at Kasr-el-Nil is 403 metres between the abutments and the smaller bridge is 178 metres, making a total width of 581 metres. The width of the Kafr Zayat bridge on the Rosetta branch is 530 metres, while the old Benha bridge on the Damietta branch is 285 metres. The average depth of water in flood in the two branches may be taken as 7 metres.