THE NILE DAMS AXD RESERVOIR. 559 



of the Dam foundation in the still waters above the rubble dams, and 

 pumps were fixed to lay dry the bed of the river. This was the most 

 exciting time in the whole stage of the operations, for no one could 

 predict whether it would be possible to dry the bed, or whether the 

 water would not pour through the fissured rock in altogether over- 

 whelming volumes. Twenty-four 12-inch centrifugal pumps were pro- 

 vided to deal if necessary with one small channel; but happily the 

 sandbags and gravel and sand embankments staunched the fissures in 

 the rock and interstices between the great boulders covering the bot- 

 tom of this channel, and a couple of 12-inch pumps sufficed. The open 

 rubble dam itself, strange to say, checked the flow sufficiently to cause 

 a difference of nearly 10 feet in the level of the water above and below; 



Fig. 5. From West Bank., looking East, furing Eclipse of November 11, 1901. 



but when the up-stream sandbag dam was constructed the difference 

 was 20 feet, so that the down-stream sandbag dam was a very small 

 one compared with the other. 



The masonry of the dam is of local granite, set in British Port- 

 land cement mortar. The interior is of rubble, set by hand, with 

 about 40 per cent, of the bulk in cement mortar, four sand to one of 

 cement. All the face-work is of coursed rock-faced ashlar, except the 

 sluice linings, which are finely dressed. This was steam-crane and 

 Italian masons' work. There was a great pressure at times to get a 

 section completed before the inevitable rise of the Xile, and as much as 

 3,600 tons of masonry were executed per day, chiefly at one point in the 



