Bridewell
in England a house of correction for offenders. The name is derived from the ancient London house of correction, originally hospital founded by Edward VI. on the site of St. Bride's Well, in Blackfriars, a well known object of pilgrimage in Roman Catholic times. a problem of statical equilibrium assumes the simplest form, and the conditions of strength and stability are steadily deor rolling load on the roadway, which is heavy in proportion to the weight of the bridge, as, for example, a railway train, the conditions are involved. When the train occupies, say, only one-half of the bridge, the chain is depressed on one side, and is raised on the other side.
Thus an undulation is produced in the bridge, which, especially if the train be moving rapidly, may seriously disturb the equilibrium, and even endanger the stability of the bridge. Various combinations have been devised to overcome this difficulty. The simplest and probably the best course is to stiffen the roadway, so that the stress of the passing load may be distributed over a considerable length of chain. In this manner large railway bridges have been constructed, for example, the Roebling bridge (1855) over the Niagara, 2½ miles below the falls, having a span of 822 feet, and being 245 feet above the level of the stream. one 685,000 The Brooklyn suspension bridge, 7,232,000 across the East River, between New
35,000 York and Brooklyn, opened in 1883, is 63,637,000 built of steel. It has a central span of 1,595½ feet, and two land spans of 930 feet each; making, with approaches, a total length of 5,989 feet, or about one mile and one furlong. The anchorage at each end is a solid cubical structure of stone, measuring 119 feet way, by 132 feet the other, rising to a height of 90 feet above high water mark, weighing 60,000 tons each. The towers are 278 feet high. The weight of the whole structure suspended between the towers is nearly 7,000 tons. The stress of suspension is borne by four cables of 5,296 steel wires each, 154 inches in diameter. The foundations of the towers were laid by means of caissons and compressed air, at a level of about 80 feet below high water mark. The Manhattan Bridge (constructed 1901-1911) across the East River between New York and Brooklyn, has a river span of 1,470 feet and a shore span of 725. It is 132 feet wide.
The Queens Queensboro bridge (1901-1909) over the East River, joining New York