Ynysgau Iron Bridge
in Merthyr Tydfil
DEMOLISHED IN 1963. Many parts saved and held in storage by Merthyr Tydfil Council.
Designed by Watkin George, it features his distinctive heart-shaped motifs (on the handrail castings). Built in 1799-1800[1]. A suggestion of a heart shape also appears on cast iron handrail posts on the Watkin George's Pontycafnau Bridge, and the motif appears on the Melingriffith Water Pump.
Many of the parts were saved after demolition, and it is hoped that the bridge will be assembled in whole or part in recognition of its historical significance. Not only was it one of the earliest cast iron bridges, it is of a bold and unique design. Subsequently cast iron bridges tended to follow a familiar pattern, with curved arches for road (and later rail) bridges, and flanged plates in the case of aqueducts.
Photographs of some of the surviving components are available here. Some of the castings are clearly broken, but it is not clear how much of this damage occurred during demolition, as it is known that some of the castings had been broken and repaired when the bridge was in use.
An account of the history of the bridge was written by Leo Davies and published in 1978[2]. The bridge, of 66 - 68 ft span, was of lightweight construction, and was a bold design. It was nominally slightly arched, although the 'arch' comprised three nominally straight sections (although the centre section had a rise of 4 inches in the middle, the overall length being 22 ft 6"). The side castings were not bolted directly together, there being oak packing pieces 2.5" thick between the vertical faces.
1963 photos of bridge shortly before demolition here show that at that time the road metal had been removed, exposing the numerous cross girders. Recent photos of the parts in storage show that the cross girders are of thin inverted T section. The vertical web rises slightly towards the centre. On each side of the web, at the centre and near each end, there was a boss with a vertical dovetail groove, presumably to accommodate connectors to join each cross girder. These cross girders were probably installed when the bridge was repaired in 1852.
Photos of the original castings show that they had been cast in open moulds, with numerous craters in the upper surface caused by gas bubbles rising to the surface of the molten iron.