To illustrate the design principle behind the Forth Bridge, engineer Sir Benjamin Baker offered a personal demonstration. Sir John Fowler (left) and Baker (right) each hold two wooden poles with outstretched arms, forming two diamond shapes. When construction foreman Kaichi Watanabe sits in the center, the diamonds are prevented from tipping inward because their outer ends are anchored.
It worked. The bridge, opened in 1890, held the record as the world’s longest single cantilever bridge span for 17 years.
The Forth Bridge is a cantilever railway bridge across the Firth of Forth in the east of Scotland, 9 miles (14 kilometers) west of Edinburgh City Centre. It is considered as a symbol of Scotland, and is a UNESCO World Heritage Site.
Construction of the bridge began in 1882 and it was opened on 4 March 1890 by the Duke of Rothesay, the future Edward VII. The bridge spans the Forth between the villages of South Queensferry and North Queensferry and has a total length of 8,094 feet (2,467 m). When it opened it had the longest single cantilever bridge span in the world, until 1919 when the Quebec Bridge in Canada was completed. It continues to be the world’s second-longest single cantilever span, with a span of 1,709 feet (521 m).
Below is a gallery of some of historic photographs of the bridge under construction.