DAMS.

The disastrous failures of earth dams has excited suspicion as to the stability of such structures; but when we consider the immensity of the dams in India, our concern should be only for the care and attention given to their construction. There the material used is well puddled; then a drove of cattle is turned loose on the fill, to stamp the earth thoroughly. This method is repeated in layers until the required height is reached. Often the Sepoys do the stamping.

The Veranun reservoir dam is twelve miles in length; and the amount of earth, of which it is composed, will encircle the globe with a belt six feet in thickness.

There is a dam on the island of Ceylon made of huge stone blocks strongly cemented together and covered over with turf, making a solid barrier of fifteen miles in length, one hundred feet wide at the base, sloping at top to forty feet, and extending across the lower end of a spacious valley.

DIMENSIONS OR RESERVOIR DAMS.—(From C. H. Beloe.)

NAME OF WORKS.NAME OFMAXIMUM DEPTHRATIO OF
RESERVOIR.OF RESERVOIR.SLOPES.
INNER.OUTER.
Bolton Water-WorksHeaton.353 to 12 to 1
“ “ “Wayoh.76“2½ to 1
LiverpoolRoddlesworth.64“2 to 1
““78““
“Anglezark.35““
BradfordStuben.55““
“Chelker.36““
“Barden.68““
“Doe Park.52““
“Silsden.78““
“Gwmwith.66““
Rhyl DistrictLlanefwydd.52““
Warrington W. W.— 131½ to 1“
NAME OF WORKS.PUDDLE WALLS.WIDTHWIDTH
MAX.THICK-THICK-OF TOPOF DYE
DEPTH.NESS ATNESS ATBATTER.BANK.WASH.
SURFACE.TOP.
′ ′ ″′ ′ ″′
Bolton Water-Works6 8 341 in 1513 612
“ “ “7020 681 in 1222105
Liverpool120— 61 in 121660
“— — 61 in 1218—
“50— — — 30—
Bradford401261 in 181215
“301261 in 1212—
“641561 in 151224
“781261 in 181215
“401261 in 241215
“501461 in 181240
Rhyl District119931 in 181012
Warrington W. W.— — — — 3—

One of the recent dams of the Croton supply, made of concrete, is thirty-one feet at the base, eight and one-half feet at top, six hundred and seventy feet long, and seventy-eight feet high. The main embankment, which forms Lough Vartry of the Dublin Water-Works, is sixty-six feet high at its deepest part, and the greatest depth of water, sixty feet. It is 1,640 feet long on the top, and twenty-eight feet wide, which forms a public road. The base, at the deepest part, is 380 feet wide; the inner slope being 3 to 1, and the outer slope 2½ to 1, and the total quantity of earthwork in it is 320,000 cubic yards. The puddle wall in the embankment is six feet wide at the top (one foot below the top bank), and eighteen feet wide at the level of the old river bed. It was carried, for its entire length, down into solid rock.

The dam of Bradlee basin, Boston, is 2,000 feet in length, twenty feet wide on top, one hundred and fifty feet at the base, and greatest height thirty-five feet. In the center of the bank is a puddle wall ten feet thick at the base, and four feet at the top, founded on the rock. The earth embankment was laid in layers, well watered and rolled.

COMPARISON OF LARGE GRAVITATION WORKS.

DISTANCENO. ACRESCAPACITYHEIGHT OFCAPACITY OF
OF SRCEOF WATEROF STORAGE.SRCE ABOVEAQUEDUCTPOPULA-
INSHED.IN GALLONS.CITY DATUMIN GALLONS.TION.
MILES.IN FEET.
New York40216,844 9 billions160 92 millions1,216,500
Boston16100,000— 134 86 “412,000
Baltimore 7— 765 millions165170 “332,190
Liverpool— 10,000 4 billions— 17 “600,000
Manchester1819,390 6 “790 39 “750,000
Glasgow[1]25¾47,800 12 “— 50 “550,000
Dublin21.614,080 2½ “692 20 “330,000

[1] Gorbals not included.

The dam for diverting the waters of Gunpowder Falls, for supply of Baltimore, is built of rubble and white marble upon solid rock. Thickness at base is sixty-two feet; depth of foundation below original surface is thirteen feet; width of the overflow is three hundred feet. The wings extend into the hill on each side two hundred and fifty-six feet. The height from the extreme foundation to the overflow is twenty-nine feet. The filling of the clay and earth on the inside is forty-five feet at the base.

Liverpool, Eng., designs constructing a masonry dam, at the source of the new supply in Wales, eighty-four feet in height.