492 



FORESTRY AND IRRIGATION, 



December, 



23 X 6}^ feet, and 40 at a higher level, 

 11^x6^ feet, giving a sluiceway of 

 24,000 square feet. 



The question of the height of the 

 clam involved a vexatious problem ; the 

 island of Philse, which lies just above 

 the cataract, contains some of the best- 

 preserved temples and buildings of 

 ancient Egypt. Mr. Willcocks' plan 

 of a dam 100 feet above the zero of the 

 Assuan gauge, with a capacity of 

 85,ooo,ooo,ooocubic feet of water, would 

 submerge these temples to a depth of 

 26 feet for a portion of each year. In 

 his book upon the dam, Mr. Willcocks 

 saj^s : "The International Commission 

 held widely divergent views about 

 Philae temple. M. Boule refused to 

 have anything to do with a project 

 which in an}' wa}^ deranged the temple. 

 Signor Torricelli said that he had been 

 asked his opinion about the dam, and 

 about the dam he would give his opin- 

 ion, regardless of temples and antiqui- 

 ties, which were outside his province. 

 Sir Benjamin Baker proposed raising 

 the whole temple, like a great Chicago 

 hotel, clean above the high level of the 

 reservoir. Savants and antiquaries, 

 and many who were neither savants nor 

 antiquaries, but to whom Philse offered 

 an easy opportunity of obtaining noto- 

 riet}', all joined in the fray. Event- 

 ually, in a moment of great weakness, 

 the Egyptian Government, buoj^ed up 

 by a succession of good summers, ac- 

 cepted the lowering of the level of the 

 reservoir, so that onl}- a part of Philse 

 temple should be drowned. The new 

 reservoir level was to be 26 feet below 

 that hitherto proposed and the capacity 

 of the reservoir was to be reduced from 

 85,000,000,000 to 35,000,000,000 cubic 

 feet of water. Fortunatel}' the condi- 

 tions of stability laid down by the Inter- 

 national Commission on the initiative of 

 Signor Torricelli were so severe that I 

 was able to design a dam nominally 

 capable of holding up 35,000,000,000 

 cubic feet of water, but actuall}- strong 

 enough to hold up 70,000,000,000." 



The dam is located five miles south 

 of Assuan, or about 550 miles south of 

 Cairo, at the head of the first cataract. 

 At this point the Nile falls about 16 

 feet in four miles, the bed of the river 



being granite rock. The fall is so 

 slight that the cataract through most 

 of the year is practicall}" no more than 

 rapids. The Nile boats go down the 

 rapids and are towed up at nearlj' all 

 stages of the river. 



The dam is almost exactly one and a 

 quarter miles long and has a maximum 

 height above the foundation of 147 feet. 

 The foundation was laid upon solid 

 granite throughout. The rock was de- 

 composed to a great depth ; in some 

 cases as much as 45 feet were removed 

 before solid rock was found. This 

 large amount of excavation increased 

 the actual cost of the work be3'ond the 

 original estimate. No drill-holes were 

 made in the underlying rock before the 

 work of construction was commenced, 

 so that the information upon which the 

 original estimate was made was not as- 

 complete as it might have been in this 

 respect. The dam is 23 feet wide at 

 the top and allows for a roadway 13. 

 feet wide, on which is laid a narrow- 

 gauge track. The rock is granite, 

 quarried near by, and laid in Portland 

 cement. It is said that 600,000 barrels 

 of cement were used in this masonry 

 an order sufficient!}' large to materially 

 affect the market value of cement in 

 England. It is interesting to note that 

 although the volume of masonry is very 

 large, yet it approximates only one- 

 fourth of the cubic contents of the 

 Great Pyramid near Cairo. 



The building of the dam was rendered 

 especially difficult by the high floods 

 which annually come down the Nile. 

 The normal difference in level between 

 high and low water at Assuan is 38 feet, 

 and work could be carried on to advan- 

 tage only during low water. 



To expose a portion of the river bed, 

 dikes were built, and the portion of the 

 bed thus laid bare was excavated to solid 

 rock. The foundation was then built 

 up to about normal flood level, and a 

 new portion of the bed dried. In this 

 manner the foundation was completed 

 across the river, and later the super- 

 structure was added to the desired 

 height. As will be seen by the accom- 

 panying illustrations, there was a great 

 deal of hand labor, as many as 12,000 

 workmen being employed at one time, 



