Bridges presentation
Following the construction of the Iron Bridge at Coalbrookdale, Thomas Telford, a gifted, self-
educated Scottish engineer, built a number of cast-iron arches throughout the British Isles. These
included canal aqueducts, which were extraordinarily innovative arrangements in which the cast iron
had real structural value. On both the Longdon-on-Tern (1796) and the Pontcysyllte (1805)
aqueducts, the cast-iron sections that formed the side walls of the trunk were wedge-shaped,
behaving like the voussoirs of a stone-arch bridge and bolted through flanges. Telford's most
ambitious notion, however, was his proposal of 1800 for a single cast-iron arch of 600ft (183m) span
over the Thames to replace Old London Bridge. An earlier proposal was unveiled in France by
Montpetit in 1779 for a bridge of 400ft (122m) over the Seine, thought to have been the inspiration
for Telford's idea. Even the young United States got into the act when Thomas Paine, the political
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