254 



ENGINEERING IN 1892. 



MASONRY DAM IN TEXAS. 



for the criticism of his professional brethren. 

 The lower face of the dam, on its down-stream 

 side, has a curve of 31 feet radius, tangent at 

 its lowest point to the water surface. The cen- 

 tral part of this face has a batter of 4| inches to 

 the foot. The profile at the top terminates the 

 down-stream face and crest of the dam with a 

 curve of 20 feet radius. To this both the front 

 batter and the surface of the pond at the crest 

 level are tangent. The upper angle of the crest 

 is rounded off with a smaller curve, and the 

 whole front of the masonry becomes a sort of 

 reversed ogee a form probably as well adapted 

 as any to pass a large volume of water from a 

 great height. The surface curve conforms as 

 closely as possible to that taken by a stream in 

 flood when it passes a low perpendicular fall. 

 At the higher flood stages it is expected that 

 there will be a tendency to a vacuum under the 

 curved stream immediately after it has passed 

 the crest. This, together with the pressure of 

 the atmosphere upon the surface of the water, 

 will keep the full flood stream in close contact 

 with the curved face of the dam, and cause it, 

 even in the heaviest flood, to slide smoothly over 

 the masonry surface to its rock foundation. Such 

 is the theory of the engineers ; but only the test 

 of time can decide how successfully they have 

 estimated the forces with which they have to 

 deal. The body of the work is in limestone 

 rock ; the two faces, the toe and the crest, where 

 the greatest wear and tear will occur, are of 

 granite, the blocks forming the cap being as 

 large ns can be conveniently handled. The en- 

 tire work is laid in hydraulic cement. It is 

 1,200 feet long, 60 feet high, and 16 feet wide at 

 the top, increasing downward till its width at 

 the bottom is 50 feet. It is intended to allow a 

 depth of 16 feet of water on the crest, and the 

 abutments at either end rise to more than that 



height. At one end of the dam the natural rock 

 rises far higher, and at the other end is an artifi- 

 cial bulkhead, containing the gatehouse and the 

 necessary sluices. The dam is 2 miles above the 

 city of Austin, and when completed will form a 

 lake 25 miles long and from half a mile to a 

 quarter of a mile wide. J. R. Frizzell is chief 

 engineer, with T. J. Fanning assistant. 



Masonry Dam in India. The largest stone 

 dam in the world has lately been finished in In- 

 dia, designed for the supply of water to the city 

 of Bombay. The work stretches across the Tan- 

 sa valley, about 65 miles north of Bombay. The 

 dam is 2 miles long, 118 feet high, 100 feet thick 

 at its greatest depth, and 15| feet wide at the 

 top. When filled, the dam will form a lake 

 covering 8 square miles, and the expected wa- 

 ter supply will be at the rate of about 100,- 

 000,000 gallons a day throughout the year. 

 More than five years have passed since the work 

 of construction was begun, and from 9,000 to 

 12,000 men, with 800 carts and animals, have 

 been employed upon it during each working sea- 

 son. Great difficulties of construction were en- 

 countered. Sand and cement had to be trans- 

 ported for a long distance ; nearly 15,000,000 cu- 

 bic feet of rubble were used, with 2,200,000 

 cubic feet of lime and nearly 3,350,000 cubic feet 

 of washed sand. The rock excavations alone 

 amounted to more than 6,700,000 cubic feet, and 

 the completed masonry altogether contains about 

 11,000,000 cubic feet. The contractors were 

 Glover & Co., of Edinburgh, and the executive 

 engineer was J. B. Clark. From the dam to 

 Bombay the water is led in iron pipes 48 inches 

 in diameter. Fortunately, in this climate the 

 pipes can be laid above ground without dan- 

 ger from frost. Each length of pipe weighs 

 about 4 tons, and their aggregate weight is 

 50,000 tons. 



