Dublin is supplied through 30,336 yards of 33-inch and 8,272 yards of two lines of 27-inch cast-iron pipes--20,000 yards laid through private property. The average fall is 20 feet per mile. There are three relief-tanks on line of 33-inch pipe. The capacity of this pipe was calculated at sixteen millions per day, while the actual delivery exceeded twenty millions. Toronto is supplied by a 4-foot wooden pipe, 7,000 feet in length, under pressure. Manchester, N. H., has a wooden penstock, six feet in diameter, 600 feet in length, that conveys supply to water wheels, under a head of twelve feet at entrance and thirty-eight feet at outlet. The new conduit for water supply of Baltimore is a continuous tunnel, seven miles long, running from the dam to the receiving reservoir--“Lake Montebello.” In its construction no open cuts were made; all work being done by drifting. Its depth below the surface of ground varies from 65 to 360 feet. The internal diameter is 12 feet; the fall is one foot per mile; capacity 170 millions daily. Fifteen shafts were sunk during the constructive work. Two miles of the tunnel were through material that required to be arched with brick; the remaining distance was through very hard rock that did not require arching. The cost of this structure was about two millions of dollars. Chicago has two tunnels under Lake Michigan, parallel with each other, 46 feet apart, extending to a crib, located in the lake, two miles from the shore. The first one was started, in 1864, under adverse criticism, and successfully completed in 1867. The cost, with the crib, was $457,800. It is five feet horizontal diameter, and 5′ 2″ vertical diameter, and made of brick. The second one was built in 1872-’74; is five feet in diameter, lined with brick. It extends from the North Side Works, a further distance of 20,000 feet, under the city and Chicago River to West Side Works. The cost of this tunnel, under the river, was $414,000, and under the city $543,000. The nature of the excavation was generally through stiff blue clay with occasionally pockets of quicksand. The Sudbury conduit, of Boston Water-Works, is sixteen miles long, with a grade of 1.056 feet per mile. The top is a semicircle of nine feet diameter, and the bottom is an arc of 13.22 feet radius, struck from a center 5.53 feet above the crown of the arch. The sectional area is 56.75 square feet. The foundation is of concrete; the side walls and spandrel backing of rubble stone masonry; the lining of brick, four inches thick, and the arch of brick, twelve inches thick. The Charles River is crossed by a granite bridge, 475 feet long and 75 feet high, with two segmental and five semicircle arches. On the line of the Vanne conduit there is an aqueduct made entirely of “beton,” which spans the valleys and quicksands in the great forest of Fontainebleau, between La Vanne River and Paris. CONDUIT DATA.--(_From Fanning._)