Early Bridges of the Stockton & Darlington Railway

Introduction

As part of the Heritage Action Zone project for the Stockton & Darlington Railway (S&DR), Listed Building and Scheduled Monument assessments were carried out along the 1825 main line. This provided an opportunity to compare the designs of bridges revealing new insights into their histories which had been missed by previous assessments undertaken in isolation. Along the original route of the S&DR, a dozen bridges dating to the 1820s and 1830s were inspected including the monumental and innovative along with several previously thought to be much later and ordinary but now shown to be of special interest.

Skerne Bridge

When the S&DR opened in 1825, its most impressive stone structure was the bridge over the River Skerne on the northern outskirts of Darlington Remarkably this remains in use as part of the national rail network and has carried trains constantly over the last 200 years.

George Stephenson had planned to build an iron bridge here. However rising prices of iron prompted Stephenson to suggest in October 1824 that the County Durham Surveyor of Bridges, the architect Ignatius Bonomi, should be asked to design a masonry structure to span between the abutments that had been started that summer (Skeat 1973, p76). The company had asked Stephenson twice earlier in the year to consult Bonomi over the bridge: they readily took up this suggestion, perhaps relieving their nervousness about trusting Stephenson’s cutting-edge approach for such a vital bridge, and duly commissioned Bonomi for a design which appears to have been produced in just a week. Construction started the following spring, and the final bills were paid for the completed bridge in June 1825.

The expectation in 1824 was that the line would transport about 10,000 tons of coal a year, but by mid-1828 over 50,000 tons had been carried in the previous 12 months, with traffic continuing to grow, nearly all of it passing over Skerne Bridge. The earthwork embankments supporting the track and the bridge’s abutments started to fail: in 1829 the S&DR’s Inspector of Masonry, John Carter, added curving wing walls to either side of the bridge to support the embankments (Boyle, 2017). The current wing walls, built of rock-faced rusticated stonework contrasting with the smoothly finished stone of Bonomi’s original bridge, are thought to be later strengthening works, quite possibly concealing Carter’s wing walls which may remain embedded in the enlarged embankments behind.

Not the World’s First Iron Railway Bridge

Although Stephenson did not build an iron bridge over the Skerne, he did build a smaller one to cross the River Gaunless near West Auckland.

This has been claimed as the world’s first iron railway bridge but is pre-dated by the Pont y Cafnau (1793) and the Afon Cynon bridge, Aberdare (1811) both built in South Wales for plateways (early railways with rolling stock guided by flanged plates instead of edge rails). Gaunless Bridge was not designed to carry locomotives – it is on the short, horse-drawn level section of line between the Etherley and Brusselton inclines and was bypassed in 1856 with the opening of a new branch line. Stephenson’s iron structure was dismantled in 1901 and replaced by a steel beam bridge reusing the original stone abutments, which allowed the crossing to be used by locomotives serving a newly opened coal mine south of the river.

Stephenson’s iron bridge, however, was preserved, eventually passing into the collection of the National Railway Museum. Recently restored and repainted in its original colours, it is now on display at Locomotion, Shildon.

Stephenson’s design is remarkable, employing both cast and wrought- iron components which slot together without requiring bolts. The bridge uses an innovative form of lenticular (lens-shaped) truss that acquires its strength from the upper members (or chords) being in compression and the lower in tension, cancelling out the compressive and tensile forces and therefore exerting only vertical forces on the piers. The iron structure is freestanding and did not rely on the masonry abutments either side of the river. These abutments, which form the terminals of the railway embankments approaching the river, still survive and form part of a scheduled monument  which also includes two conventional masonry bridges over streams, Oakley Cross and Hummer Beck.

These bridges, also attributed to Stephenson, are the least altered bridges on the entire line built for the 1825 opening.

Accommodation Bridges

The Brusselton Accommodation Bridge was previously dated to 1825 and attributed to Stephenson. Its design is quite different to the line’s original masonry bridges which feature roll-moulded arch rings and is now known to have been designed by Thomas Storey and built in 1832-1833. It was one of two bridges built for the owner of the land that was divided by the western Brusselton Incline. The opening of the Haggerleases branch line in 1830 to collieries on Cockfield Fell had increased the traffic on the incline: perhaps stoppages caused by cows crossing the line had become a problem. 

Economies in construction: dual and single lines

The need to provide accommodation crossings for owners whose land was bisected by the railway was one of the costs that the S&DR had underestimated. Although the line was designed and was mainly built to be dual-tracked, economies were made during construction. Only a single line was laid, with frequent passing loops, and although cuttings and embankments were sized for dual tracks, most bridges were built for just a single line.

In the early 1830s the locomotive-hauled line running east and south from Shildon to the Tees at Stockton was upgraded to dual tracks and the original sleeper stones of the western end of the line (which had two holes for rail fixings) were replaced with larger, four-holed blocks. This dualling of the line resulted in the widening of underbridges, carrying the railway line, to take two tracks such as the accommodation bridge near Dene Beck  and in Darlington.

Overbridges

The original bridges built to carry roads and paths over the railway (overbridges) had been built to span a single line: these had to be completely rebuilt to span the dual line. Between Newton Aycliffe and Darlington there were five identical overbridges which had been assumed to date to the late 19th century because of their rock-faced stonework.

The bridge at Simpasture Junction was rebuilt after a railway accident and that at Codling Beck was demolished in 2012, leaving three survivors. These all have narrow-waisted plan forms and restricted clearance of just 21 feet 10 inches (about 6.7 metres) all indicating an early date. The demolition rubble of Codling Bridge also included reused two-holed sleeper stones, suggesting that all of these bridges were those mentioned in company minutes in 1831-33 that were designed by Thomas Storey when the line was re-laid as dual track.

All three survivors are now listed, the best example being Little Whessoe occupation bridge. Interestingly, the stonework is very similar to that of Skerne Bridge’s current wing walls, suggesting that these might also be earlier than previously thought.

Company organisation

As a pioneering railway, the S&DR’s approach to running their business evolved and was not fixed. Individuals were sometimes directly employed but were often working as contractors or sub-contractors. Subsidiary companies were also often set up to build new infrastructure expanding the network. All this led to increasing amounts of variability in designs in later years as can be seen with the S&DRs extension up Weardale (See Marcus Jecock's article in this issue).

Impact of our research

The research undertaken as part of the Heritage Action Zone project has resulted in a greater understanding of the surviving early-19th century bridges of the S&DR, all built during the pioneering phase of railway development when Britain led the world in this vital new technology. Alongside updated descriptions of existing designations, our improved understanding has led to five new listings, helping to preserve these often modest and overlooked elements of the famous railway.

Further information

Boyle, B. (2017) 'John Carter and the Saving of the Skerne Bridge' in The Globe Vol 3, pp3-9.

Skeat, WO (1973) George Stephenson the Engineer and his Letters

Download this issue of the research magazine as a PDF