The 2.5 km. (1.5 mile) Forth Railway Bridge, the world’s first major steel bridge, with its gigantic girder spans of 521 m. (1710 ft.) ranks as one of the great feats of civilization. It was begun in 1883 and formally completed on 4 March 1890 when HRH Edward Prince of Wales tapped into place a ‘golden’ rivet.
Tancred–Arrol, constructed the bridge, robustly designed in the aftermath of the Tay Bridge disaster by civil engineers Sir John Fowler and Benjamin Baker. The balanced cantilever principle was adopted. The main crossing comprises tubular struts and lattice-girder ties in three double-cantilevers each connected by 105 m. (345 ft.) ‘suspended’ girder spans resting on the cantilever ends and secured by man-sized pins. The outside double-cantilever shoreward ends carry weights of about 1000 tonnes to counter-balance half the weight of the suspended span and live load.