192 Sir Benjamin Baker [June 6, 



On February 12, 1899, the foundation stone of the Dam was laid by 

 H.R.H. the Duke of Connaught. Many plans were considered by the 

 engineers and contractors for putting in the foundations of the Dam 

 across the roaring cataract channels, and it was finally decided to 

 form temporary rubble dams across three of the channels below the 

 site of the great Dam, so as to break the force of the torrent and get 

 a pond of comparatively still water up stream to work in. Stones of 

 from 1 ton to 12 tons in weight were tipped into the cataract, and 

 this was persevered with until finally a rubble mound appeared above 

 the surface of the water. The first channel was successfully closed 

 on May 17, 1899, the depth being about 30 ft. and the velocity of 

 current nearly 15 miles an hour. In the case of another channel, the 

 closing had to be helped by tipping in railway wagons themselves, 

 loaded with heavy stones, and bound together with wire ropes, 

 making a mass of about 50 tons, to resist displacement by the torrent. 



These rubble dams were well tested when the high Nile ran over 

 them ; and on work being resumed in November, after the fall of the 

 river, water-tight sandbag dams or sudds were made around the site 

 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 overwhelming volumes. Twenty-four 12-in. centrifugal 

 pumps were provided 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 bottom of this channel, and a couple of 12-in. 

 pumps sufficed. The open rubble dam itself, strange to say, checked 

 the flow sufficiently to cause a diflerence of nearly 10 ft. in the 

 level of the water above and below ; but when the up-stream sand- 

 bag dam was constructed the difference was 20 ft., 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 

 Portland 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 

 Nile, and as much as 3600 tons of masonry were executed per day, 

 chiefly at one point in the Dam. A triple line of railway, and 

 numerous trucks and locomotives, were provided to convey the 

 materials from quarries and stores to every part of tlie work. The 

 maximum number of men employed was 11,000, of whom 1000 were 

 European masons and other skilled men (Figs. 3, 4 and 5). 



Mr. Wilfred Stokes, chief engineer and managing director of 

 Messrs. Kausomes and Rapier, was responsible for the detailed 



