556 POPULAR SCIENCE MONTHLY. 



by Sir Samuel Baker more than forty years ago, from mere inspection 

 of the site without surveys. In suggesting a series of dams across the 

 Nile to form reservoirs from Khartoum downwards, he wrote: "The 

 great work might be commenced by a single dam above the first cataract 

 at Aswan, at a spot where the river is walled in by granite hills. By 

 raising the level of the Nile 60 feet, obstructions would be buried in 

 the depths of the river, and sluice-gates and canals would conduct the 

 shipping up and down stream." This single dam, proposed by Sir 

 Samuel Baker forty years ago, is in effect the one which is now on the 

 point of completion. Mr. Willcocks' original design consisted prac- 

 tically of a group of independent dams, curved on plan, and the 

 arrangement of sluices and dimensions of the dam differed consider- 

 ably from those of the executed work. There is no doubt that the single 

 dam, 114 miles in length, constitutes a more imposing monumental 

 work than a series of detached dams, and that it also offered greater 

 facilities to a contractor for the organization of his work and rapid 

 construction ; and, further, the straight dam is better able to resist tem- 

 perature stresses from extreme heat without cracking. Two dams 

 across the Nile, the old barrage and the Asyut Barrage, have already 

 been described; and it will be hardly necessary to say, therefore, that 

 the Aswan Dam is not a solid wall, but is pierced with sluice openings 

 of sufficient area for the flood discharge of the river, which may 

 amount to 15,000 tons of water per second. There are 180 such open- 

 ings, mostly 23 feet high by 6 feet 6 inches wide; and where subject 

 to heavy pressure, when being moved, they are of the well-known Stoney 

 roller pattern. 



Although the preliminary studies of Mr. Willcocks and the other 

 government engineers occupied some four years, there was neither 

 time nor money to sink shafts in the bed of the river, to ascertain the 

 real character of what was called in the engineer's report 'an extensive 

 outcrop of syenite and quartz diorite clean across the valley of the 

 Nile,' giving 'sound rock everywhere at a very convenient level.' Un- 

 fortunately, the rock proved to be unsound in many places to a consider- 

 able depth, with schistous micaceous masses of a very friable nature, 

 which necessitated carrying down the foundations of the dam some- 

 times more than 40 feet deeper than was originally anticipated or pro- 

 vided for in the contract. As the thickness of the dam is nearly 100 

 feet at the base, this misapprehension as to the character of the rock 

 involved a very large increase in the contract quantity and cost of the 

 granite masonry of the dam. The total length of the dam is about 

 l 1 /^ miles; the maximum height from foundation, about 130 feet; the 

 difference of level of water above and below, 67 feet; and the total 

 weight of masonry over one million tons. Navigation is provided for 

 by a 'ladder' of four locks, each 260 feet long by 32 feet wide. 



