In May, 1811, a Bill was passed for the erection of a new bridge to cross the Thames about a quarter of a mile west of London Bridge, and to be known as Southwark Bridge. The work was undertaken by a private company, and the cost stated to have been about £800,000, though it would appear from contemporary records to have been considerably less. The architect, John Rennie, F.R.S. (who afterwards built New London Bridge), designed a bridge of three cast-iron arches, the two outer and smaller spans being 210 feet long, while the central and largest arch covered 240 feet (73 m). The height of this arch from the water at the highest spring tides was about 42 feet. The roadway was formed of solid plates of cast iron joined by iron cement. This roadway, 42 feet wide was supported by stone piers, which rested upon timber platforms whose foundations of wooden piles were driven below the bed of the river. A new and successful principle in the construction of cast-iron bridges was introduced in this instance by Rennie, namely, the formation by the ribs of the arches of a series of hollow masses, or voussoirs, similar to those of stone. Bolts are rendered unnecessary by the use of dove-tailed sockets and long cast-iron wedges, and the whole mass is closely tied together by bondstones, vertical and horizontal, that it is well fitted to resist the horizontal thrust. The entire length of the bridge was 700 feet, and the weight of the iron-work 5,700 tons.
Although the Bill for the erection of Southwark Bridge passed in May, 1811, the works were not begun till 1813; they were finished six years later. The first stone was laid by Admiral Lord Keith, April 23rd, 1815, and the final ceremony took place under peculiarly impressive circumstances on March 24th, 1819, the bridge, illuminated with lamps, being declared open as St. Paul’s clock tolled midnight.
Although built with the avowed intention of relieving the surplus traffic of London and Blackfriars Bridges, it was estimated by Bennoch that the number of vehicles and passengers over Southwark Bridge averaged less than one-fortieth of the traffic of its sister bridge to the east; London Bridge indeed was only relieved by Southwark Bridge to a very slight extent, and the congestion of traffic was almost as great as before. Several reasons were advanced for the comparative failure of Southwark Bridge. First, the payment of toll, which naturally tends to drive traffic (especially vehicles) over the free bridges. Secondly, a bad approach from the south side. Thirdly, the want of direct communication with the main arteries of the City on the north side of the bridge. Fourthly, the steepness of the approaches to the bridge, and the actual narrowness of the bridge itself.
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