to the opposite side in order to secure deep water in front of Rameses’ temple of Jerf Husain (“Jerf” means steep, scoured bank). The spurs have been constructed with care, and as the courses of roughly-dressed stone can be examined at fairly low water (I have never seen them at absolutely low water) it is evident that there has been no great degradation of the bed during the last 2,000 or 3,000 years. The first, or Assuân Cataract, has a drop of 5 metres on a length of 5 kilometres. From Khartoum to Assuân, on a total length of 1809 kilometres, there are 565 kilometres of so-called cataracts with a total drop of 192 metres, and 1,244 kilometres of ordinary channel with a total drop of 103 metres. At the head of the 1st Cataract is the Assuân dam, regulated on for the first time in October 1902. It has 140 openings of 2 metres × 7 metres and 40 openings of 2 metres × 3¹⁄₂ metres. At the foot of the 1st Cataract, opposite the town of Assuân, on the Island of Elephantine, has stood a Nile gauge from very ancient times. An officer belonging to the Roman garrison in the time of the Emperor Severus marked an extraordinarily high flood on the gauge. The maximum flood-mark at the time of the visit of Napoleon’s French savants was however 2.11 metres higher than the above. As the middle of Severus’ reign was A.D. 200, and the visit of French savants A. D. 1800, they concluded that the bed and banks of the Nile had risen 2.11 metres in 1600 years or 0.132 metres per 100 years. The new gauge divided into cubits and twenty-fourths was erected in 1869 and has been recorded daily since then (a cubit = 54 centimetres). The accidental zero of the gauge is R. L. 84.16. The mean low-water level or true zero is R. L. 85.00. [Illustration: PLATE X. LONGITUDINAL SECTION OF THE NILE FROM WADY HALFA TO GEBEL SILSILAH Lith. Sur. Dep. Cairo. CROSS SECTION OF THE NILE VALLEY NEAR IBRÎM CROSS SECTION OF THE NILE VALLEY NEAR ASSUÂN TYPICAL CROSS SECTION UPSTREAM OF ASSUÂN DAM]