1902.] on the Nile Dams and Beservoir. 189 



with cemented joints. This piling extends into the sand bed of the 

 river to a depth of 23 ft. below the upper surface of the floor, and 

 thus cuts off the water and prevents the undermining action which 

 caused so much trouble and expense in the case of the old barrage. 

 The height of the roadway above the floor is 41 ft., and the length 

 of the piers up and down stream 51 ft. The river bed is protected 

 against erosion for a width of 67 ft. up stream by stone pitching, 

 with clay puddle underneath to check infiltration, and down stream 

 for a similar width by stone pitching, with an inverted filter-bedl 

 underneath, so that any springs which may arise from the head of 

 water above the sluices shall not carry sand with them from under- 

 neath the pitching. 



It is easy enough to construct dams and barrages on paper, but 

 wherever water is concerned the real difficulty and interest is in the 

 practical execution of the works, for water never sleeps, but day and 

 night is stealthily seeking to defeat your plans. On the Nile the 

 conditions are very special, and in some respects advantageous. 

 There is only one flood in the year, and within small limits the time 

 of its occurrence can be foretold, and arrangements made accordingly. 

 It would have been impossible to have carried out the Nile works 

 on the system adopted had the river been subject to frequent floods. 

 The working season for below-water work on the Nile lies practically 

 between November and July, for nothing would be gained by start- 

 ing the temporary enclosing embankments, or sudds, when the river 

 was at a higher level than it is in November; nor would it be pos- 

 sible at any reasonable cost to prevent the sudds from being swept 

 away by the flood in July. At Asyut the mode of procedure was to 

 enclose the site of the proposed season's work by temporary dams or 

 sudds of sandbags and earthwork, then to pump out and keep the 

 water down by powerful centrifugal pumps, crowd on the men, exca- 

 vate, drive the cast-iron sheet piling, build the masonry platform 

 and piers, lay the aprons of puddle and pitching, and get the work 

 some height above low Nile level before the end of June, so that 

 the temporary dams should not require reconstruction after being 

 swept away by the flood. The busiest months were May and 

 June, when in the year 1900 the average daily number of men was 

 13,000. It is also then the hottest : the shade temperature rising to 

 118 degrees. To keep the water down, seventeen 12-in. centrifugal 

 pumps, throwing enough water for the supply of a city of two mil- 

 lion inhabitants, had to be kept going, and in a single season as 

 many as one and a half million sandbags were used in these tem- 

 porary dams. The bed of the river being of extremely mobile sand, 

 the constant working of the pumps occasionally drew away sand from 

 under the adjoining completed portions of the foundations, necessi- 

 tating the drilling of many holes through the 10-ft. thick masonry 

 platform, and grouting under pressure with liquid cement. About 

 1000 springs also burst up through the sand, each one of which 

 required special treatment. A new regulator had to be constructed 



