256 



ENGINEERING. 



to escape, but, if not, they must take their 

 chances. 



Of modern dams, that at Fureus is the most 

 famous of those actually finished. It was built 

 from designs by Messrs. Graiff and Grand- 



FEET 

 277 



250- 



200- 



150- 

 IOO- 



1. QUAKER 



2. Fun cms 



3. GH.EPPC 



4. VYRNWV 



5. PUCNTE-S 



6. VAU o' INFERNO 



SECTIONS OF GREAT DAMS. 



Champs between the years 1859 and 1866, and 

 was intended partly to protect the town from 

 freshets, and partly to afford a perennial water- 

 supply. Its cross section is shown in the en- 

 graving. Its plan is a curve on a radius of 

 828 feet from a center on the down-stream 

 side. It is founded on compact granite, a 

 trench 3 feet deep having been quarried out to 

 prevent slipping. The material is rubble ma- 

 sonry, laid in courses of 5 feet, and carried up 

 to a height of 184 feet. At the 

 base it is 110 feet thick, and 9 feet 

 8 inches at the crest. The calcu- 

 lations aimed for a pressure of 

 about 95 pounds to the square inch. 

 The dam contains about 52,000 cu- 

 bic yards of masonry, and the cost 

 of erection was $180,400. The ca- 

 pacity of the reservoir is 352,000,- 

 000 gallons. The reservoir dis- 

 charges its surplus water through 

 two tunnels, leading through a hill 

 into an adjacent valley, where such 

 power as is constant is usefully 

 employed. 



Another famous structure is the 

 Gileppe Dam at Verviers, Belgium, 

 No. 3. It was finished in 1875, 

 under the supervision of M. Bod- 

 son. It differs largely from the 

 Furens section, and, indeed, from 

 the best theories of dam-construc- 

 tion. This was rendered neces- 

 sary by the anxiety of down-stream 

 residents, who strongly opposed 

 the construction of the dam, on 

 the ground of danger. It is laid 

 on an arc, described by a radius of 1,640 feet, 

 with a length of 771 feet. The reservoir con- 

 tains 2,701,687,000 gallons, nearly eight times 

 as much as the reservoir at Furens. The foun- 



dations are carried down into solid rock. Its 

 total height is 154 feet, and the width of the 

 crest, which carries a roadway, is 49 feet. 

 The base is 216 feet thick. The outlet pipes, 

 always a source of danger, are carried through 

 a hill at some distance from the end of the 

 dam. 



Another great Spanish dam is on the river 

 Lozoyers, and supplies water to the city of 

 Madrid. It is known as the Villar Dam. The 

 capacity of its reservoir is 4,400,000,000 gal- 

 lons, nearly thirteen times that of Furens. It 

 is built on a sharp curve, the radius being 440 

 feet, and the length of the dam, on the crest, 

 546 feet. A curve like this probably adds con- 

 siderably to the strength of a short dam. The 

 material is rubble masonry in hydraulic mor- 

 tar, costing $402,780. 



The Vyrnwy Dam, shown in section in No. 

 4, crosses the Vyrnwy river in North Wales. 

 The area that will be flooded is, or was, a 

 charming region, largely occupied by villas and 

 country-seats, and, of course, involving a large 

 amount of outlay in property rights. The dam 

 will impound an area of 1,115 acres. It is 

 1,255 feet long, built of Cyclopean rubble set 

 in rnortar, and with the interspaces filled with 

 cement-concrete. The individual masses weigh 

 from 2 to 8 tons each, and it is calculated that 

 this method of construction will give excep- 

 tional solidity to the wall. The upper face of 

 the dam is coated with cement. The height 

 is 146 feet, and the breadth at base 117 feet 9 

 inches. 



A large dam is building at San Mnteo, Cal., 



G\OG-E DAM 



CROTON WATEU-SHED. 



designed for the water-supply of San Francisco. 

 It is 170 feet high, 176 feet thick at the base, 

 and 20 feet wide, being in shape very much 

 like a truncated pyramid. 



