Engineering marvel of Forth Bridge celebrated at National Library
One of the world's greatest feats of engineering is being celebrated at the National Library of Scotland with a special free display ['The Forth Bridge: Building an icon'] marking the construction of the Forth rail bridge.
When it opened 125 years ago, it had the longest cantilever bridge span in the world and was the first major construction in Britain to be built of steel. The bridge reaches 110 metres (361ft) above high water with foundations that are sunk 27 metres (89ft) into the river bed. It is made up of some 53,000 tonnes of steel, including 6.5 million rivets.
The final rivet was driven home by the Prince of Wales, later King Edward VII, on 4 March 1890, signalling the start of train operations across a structure that has become one of the most famous in the world.
The National Library is displaying many fascinating items from its collections to tell the remarkable story of the bridge's eight-year-long construction which involved 4,600 workers at the peak of activity. The items range from detailed plans and photographs of the construction to an original copy of the menu that was served to guests at the royal opening.
Work on the bridge was often a dangerous enterprise with men dangling on ropes to work on the structure. Falls were common, resulting in one safety measure being introduced. Boats patrolled underneath the site to rescue anyone who fell but this did not prevent fatalities. At least 57 deaths are recorded, although this is thought to underestimate the true number.
The bridge has its origins in the Forth Bridge Railway Act of 1873, when construction was authorised to a design of railway engineer Thomas Bouch. He had designed the Tay Bridge which opened in 1878. However, a section of the bridge collapsed in a gale the following year, ending Bouch's involvement in the Forth Bridge.
A new cantilever design by Benjamin Baker and Sir John Fowler, who had worked together on the early underground railway system in London, was then put forward. Baker devised a human cantilever using three members of his staff to demonstrate the load bearing principle of the design at a lecture to the Royal Institution in London.
The design was accepted and work began in 1882. One of the major engineering challenges was the construction of the stone piers on which the bridge's superstructure would sit. In some sections, dams could be built to push out the river water and allow the foundations to be laid. Elsewhere, it required a more elaborate solution.
Enormous wrought iron cylinders called caissons measuring 21 metres (70ft) in diameter were made, floated into position and then weighted with cement until they sat on the river bed. This allowed the men to work at the base within the sealed caisson almost like coal miners within a mine. Air was pumped in for them to breathe. This work was contracted to a French firm and was mainly carried out by Italian, Belgian, Austrian and German labour.
Alison Metcalfe, Manuscripts Curator at the National Library of Scotland who has organised the display, said: 'The Forth Bridge has become a prominent Scottish landmark but perhaps we have lost sight of just how much of an engineering marvel it was 125 years ago and remains to this day. We hope this display will show some of the ingenuity involved in its construction and help to remember the sacrifice of so many who lost their lives when it was being built.'
'The Forth Bridge: Building an icon' is on from 1 April to 21 June at the National Library of Scotland, George IV Bridge, Edinburgh. Entry is free.
See also related news story.
1 April 2015