Bridges and viaducts › Forth Bridge
Forth Bridge
The cantilever bridge over the Firth of Forth, opened in 1890: three towers 361 ft (110 m) above high water, two main spans of 1,710 ft (521 m), the rail 157 ft (48 m) above the water.
- Opened
- 4 March 1890
- Line
- Edinburgh to Fife and the north
- Kind
- Cantilever (steel)
- Length
- 8,296 ft (2,529 m)
- Main spans
- Two of 1,710 ft (521 m)
- Towers
- 361 ft (110 m) above high water
- Rail
- 157 ft (48 m) above high water
- Train drawn
- ScotRail Class 170
unverified Some of these figures haven’t yet been checked against an official source or a published history. What’s in doubt ↓
Four times larger
Close up
At 10 px a metre, the scale of the train drawings, so the train is the size it is on its own page. Each is cut from the same drawing.
Sources
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- The Forth Bridge W. Westhofen, reprinted from Engineering (text on Wikisource; Plate III on Wikimedia Commons), 1890General Description of the Structure (p. 10): lengths, spans, towers, rail level, headway, cantilever depths, pier spacing
- The Forth Bridge W. Westhofen, reprinted from Engineering (text on Wikisource; Plate III on Wikimedia Commons), 1890Plate III, Figs. 1, 4, 7: the cantilever's joints, members and heights, read off Fig. 7; the tower's bracing (Fig. 4); the general elevation (Fig. 1)
- The Forth Bridge W. Westhofen, reprinted from Engineering (text on Wikisource; Plate III on Wikimedia Commons), 1890Building out of the Cantilevers (p. 47): central girders 350 ft, 40 ft deep at the ends, 50 ft at the centre, eight bays, straight bottom; end posts
- The Forth Bridge W. Westhofen, reprinted from Engineering (text on Wikisource; Plate III on Wikimedia Commons), 1890Raising of the Approach Viaduct Girders (p. 31): approach girders 21 ft deep in eight 21 ft bays; approach pier tops 130 ft 6 in above high water
- The Forth Bridge W. Westhofen, reprinted from Engineering (text on Wikisource; Plate III on Wikimedia Commons), 1890The Circular Granite Piers (p. 30); South Approach Viaduct Piers (p. 18), Table IV: circular piers 49 ft across at 12 ft 8 in above high water, tops 18 ft above high water; foundation levels
- OpenStreetMap OpenStreetMap contributors (ODbL), read 8 November 2026ways tagged bridge:support round the bridge, read 8 November 2026: check of the piers' places along the line
- Forth Bridge 2022 (photograph, from Dalmeny) Wikimedia CommonsForth Bridge 2022.jpg (Commons, CC BY-SA 4.0), read 8 November 2026: the sunlit red and granite; the end piers' towers
unverified
- The ground and the island are drawn from the plate's general elevation and the foundation levels (Table IV), simplified.
- The central girders' eight bays are drawn equal; Westhofen says only 'slightly unequal'.
- The Inchgarvie cantilevers are drawn with the Fife and Queensferry bays (Fig. 7); Westhofen gives all six as 680 ft but draws only one in detail.
- The red and the granite are read off a sunlit photograph from Dalmeny (BRG8, 8 November 2026): the lit red about #B5473B, the granite a sandy #B39467.
- The cantilever end piers' towers rise to about 200 ft above high water and are about 36 ft along the line, read off the sunlit photograph scaled by the approach girders' 21 ft; the trains pass through a portal in each.
- The approach piers' widths and taper and the arches' openings are estimated from the plate's general elevation and photographs, not from printed figures.
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