Old Iron Bridge, Merthyr Tydfil
The Old Iron Bridge of 1800, originally known simply as Merthyr Bridge before 1809, in Merthyr Tydfil, South Wales, was a cast-iron bridge across the River Taff. Although an important early example of iron bridge-building and well known as a local landmark within living memory, the bridge has largely disappeared from engineering history. Early iron bridges The Iron Bridge across the Severn near Coalbrookdale opened in 1781 and is generally regarded as the world's first cast-iron bridge. It had little immediate influence on bridge design and few other important iron bridges were built as a result. However a flood in 1795 washed away many bridges on the Severn, but the Iron Bridge survived. This survival had more influence on bridge design, as did the completion of Wearmouth Bridge the following year. Cast iron was now established as a viable material for bridges and a number were produced in the years immediately afterwards. Earlier bridges in Merthyr Richard Crawshay's Cyfarthfa Ironworks was on the West bank of the River Taff, the opposite side from the centre of the developing town. The previous stone bridge had collapsed in the winter of 1798–99. This left the only bridge across the Taff as Jackson's Bridge, which had been built in 1793 by the Dowlais Iron Company. This was an inconvenience to the inhabitants of Merthyr, many of whom now worked for the Cyfartha ironworks, who needed to cross the river to get to the works. Rivalry between the ironmasters was also intense and it was a matter of prestige for Cyfartha workers to not be dependent upon another company's bridge. Small iron bridges already existed at Merthyr, crossing the Glamorganshire Canal. This was a far smaller watercourse than the Taff and only needed a simple single-panel bridge. One of these still survives, although now only kept as a monument in a park. Construction Richard Crawshay commissioned a new bridge and had Watkin George, his principal engineer at Cyfartha and who had also designed the nearby Pont-y-Cafnau in 1792, design it. The bridge was built in 1799 and opened at the end of April 1800. The river needed a span of around , which was too much to have been cast in one piece, or then installed, with the equipment of the time. Although structurally an arch bridge, the bridge was cast in three sections, each almost straight. The outer panels were straight, the centre had a rise of in its length. The sides of the bridge were cast as three rectangular panels, including their balustrade. The ends of the arch were supported on triangular cantilever brackets, cast in two sections. The abutments of the bridge were stone, battered back with sloping faces so that they met the ends of the arch panels perpendicularly. Where the iron castings abutted against each other was packed with oak planks, two or three inches thick and the width of the iron parts. These were bolted through and clamped. The intention was to give the iron structure some degree