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Galton Bridge
Birmingham Canal, Smethwick, West Midlands, UK
Galton Bridge
associated engineer
Thomas Telford
date  1827 - 1829
era  Georgian  |  category  Bridge  |  reference  SP014893
ICE reference number  HEW 421
photo  PHEW, courtesy ICE
An elegant cast iron road bridge by Thomas Telford, over a deep cutting of the Birmingham Canal at Smethwick. Telford made improvements to the canal's route, including the creation of the cutting — one of the largest earthworks of the time — and he bridged the cutting with the longest and highest single span to that date. Now Grade I listed and closed to vehicular traffic, the bridge is used by pedestrians.
In 1824, the Birmingham Canal Company consulted engineer Thomas Telford (1757-1834) (1757-1834) on major improvements to the route of its canal between Birmingham and Wolverhampton. The canal had opened in 1772, designed by James Brindley (1716-72), and it followed the contours of the land. The highest stretch, at Smethwick Summit, had been lowered from 150m to 144m above sea level in 1789, in work attributed to John Smeaton (1724-1792). The canal was popular and becoming overcrowded, plus there was some difficulty supplying it with water.
Telford’s wider canal takes a more direct route. A major feature is the 3.66km Smethwick Cutting, constructed to enable the canal to by-pass Smethwick Summit at 138m above sea level. Galton Bridge carried the Smethwick-Sandwell road over the deepest part of the cutting. Its single cast iron arch spans 45.7m, springing from brick abutments set high on the sides of the cutting. The arch rise is about 4.6m and at midspan, and the underside of the arch is some 20m above Birmingham Canal.
The arch consists of six ribs each constructed from seven segments bolted together. The ribs and spandrels are diagonal lattices, and the space between road surface and ribs is filled by a three-dimensional array of intersecting diagonal struts. The roadway is flanked by cast iron railings, which terminate at sandstone piers at the corners of the abutments.
The bridge is named after Samuel Tertius Galton (1783-1844), a banker who served on the committee of the Birmingham Canal Navigation Company from 1815 to 1843. Its design details follow a well-known Telford pattern and share many similarities with his earlier Mythe Bridge (1826) and Holt Fleet Bridge (1828) over the River Severn.
In his autobiography (published 1838), Telford wrote: "The motive for this extraordinary span was safety, combined with economy, for if it had not exceeded the span of the other bridges across this canal, the abutments must have been founded as low as the bottom of the canal, because the bridge must have been carried 70ft [21.3m] up to the level of the top of the banks, which would have led to an immense mass of masonry liable to bulge and be overthrown in rainy seasons by the earth acquiring a hydrostatic pressure; whereas by increasing the span to 150ft [45.7m], there was opportunity of founding the abutments at a depth merely sufficient to admit of a proper iron-arch curvature; so that the proportion of masonry is small, and produces variety by its appearance of lightness, which agreeably strikes every spectator of the massive works."
In 1861, writer Samuel Smiles (1812-1904) noted that Galton Bridge "has been much admired for its elegance, lightness, and economy of material".
In August 1972, the bridge was Grade II listed. Its status was raised to Grade I in February 1989. In 1975, vehicles were stopped from crossing Galton Bridge as increases in traffic exceeded the bridge’s 2 tonne weight limit. A modern trunk road, the A4252 Telford Way, was constructed to the south east, by-passing the old bridge. The canal runs through a concrete tunnel here, with the new roadway supported on embankments.
Telford’s bridge remains open to pedestrians and is part of the cycle paths network. It lies within the Smethwick, Galton Valley Conservation Area (designated in 1984 as the Smethwick Summit Conservation Area).
Resident engineer: William Mackenzie
Contractor: Thomas Townshend
Ironwork: Horseley Ironworks, Tipton
Research: ECPK
reference sources   CEH W&WTTSmiles3

Galton Bridge