The Forth Bridge

The Forth Bridge

The Forth Bridge is a 2.5 kilometre painted steel cantilever railway bridge crossing the Firth of Forth on a north-south axis, linking Edinburgh and Fife. It was designed and tendered for in 1882 by Sir John Fowler and Sir Benjamin Baker, constructed between 1883 and 1890 by the contractors Tancred, Arrol and Co under Joseph Philips, and completed on 4th March 1890.

The bridge's structure comprises three giant cross-braced steel towers, each counterbalancing two arms on either side to provide two full cantilevered spans of 521 metres each, with a 107 metre suspended span truss at the centre, plus two half outer spans. Each tower structure is set on four circular-plan granite and concrete piers. The southern piers rest on the sea-bed, the central piers sit on a shelf of rock beside Inchgarvie in Dalmeny Parish, and the northern piers are founded on a promontory at North Queensferry.

The superstructure is flanked by approach viaducts, supported 45 metres above water level by tapering rectangular-plan masonry piers. Five piers to the north feature three masonry arches adjoining the promontory at North Queensferry, whilst ten piers to the south feature four masonry arches adjoining the promontory at South Queensferry. Trains pass through round-arch masonry portals at the innermost piers, which mark the start of the cantilever superstructure.

At Inchgarvie, a brick pier remnant from Thomas Bouch's abandoned 1879 design survives. It is surmounted by an early 20th century cast-iron leading light with sectional lantern, bracketed gallery and diamond-paned glazing.

Construction was a monumental undertaking. A workforce of five thousand laboured for seven years, using more than fifty thousand tonnes of Siemens-Martin open-hearth steel and 8 million rivets. The towers rise from massive granite piers whose underwater foundations were constructed using 21 metre-wide submersible wrought-iron cylinders called caissons, carefully positioned on the sea bed before being filled with concrete. The bridge was first built in sections on land before being disassembled and transported by boat for re-erection at the site. The principal contractor William Arrol, who was knighted in 1890, pioneered innovations including hydraulic spades and riveting machines that allowed construction to advance at an extraordinary pace. Where possible, the design utilises natural features including the promontories and high banks at North and South Queensferry and the Inchgarvie rock outcrop.

A bridge crossing the Firth of Forth was first proposed in 1818 by Edinburgh civil engineer James Anderson. The Forth Bridge Company was not founded until 1873. The original contract went to Thomas Bouch, whose design followed his scheme for the Tay Bridge. However, following the Tay Bridge disaster of 28th December 1879, when high winds destroyed the central girders and caused approximately 75 deaths, the company commissioned a completely new design.

John Fowler, knighted in 1885, had a distinguished background in railway engineering. He had previously designed the first railway bridge across the Thames in 1860, St Enoch's station in Glasgow, and served as a principal engineer of the London Underground system. His colleague Benjamin Baker, knighted in 1890, conducted experiments on wind pressure using gauges installed on the Forth shoreline in preparation for the bridge. Their innovative cantilever design achieved spans nearly four times larger than any previously built railway bridge and remains the world's longest bridge built on the cantilever principle. Construction was authorised by an Act of Parliament in 1883, and the bridge opened on 4th March 1890 with Albert Edward, Prince of Wales, inserting a final inscribed gold-plated rivet.

The bridge is distinguished by its characteristic colour, known as Forth Bridge Red, similar in shade to iron oxide, which helps conceal rust-prone areas. Seven thousand gallons of paint are required to cover the surface. Between 2002 and 2011, all earlier paint coats were removed and a new hard-wearing coating system was applied, originally developed for North Sea oil rigs and expected to last at least 20 years. The bridge has remained in continuous use since opening, with around 200 trains passing over it each day.

On completion, the Forth Bridge achieved the longest bridge spans in the world and was the largest steel structure, pioneering widespread adoption of steel in bridge construction. It stands as one of the most ambitious and successful engineering achievements of the 19th century and is Scotland's most instantly recognisable industrial landmark, becoming a symbol of national identity comparable to the Eiffel Tower in Paris.

The bridge is included on the statutory list twice, in both the City of Edinburgh and Fife Council areas, and forms a group listing with Jamestown, Forth Bridge, North Approach Railway Viaduct and Hope Street, Forth Bridge Approach Railway, Truss Bridge.