Rail’s Iron Age
Most of Britain’s wrought and cast-iron viaducts have been lost to us - casualties of the Beeching era. DR JOSEPH BRENNAN examines what now survives of this legacy and considers some of the elegant structures that should have been saved
DR JOSEPH BRENNAN studies Britain‘s wrought and cast-iron viaducts… and recalls some that didn’t stand the test of time.
When it comes to railway viaducts, especially those built in the age of steam, it is difficult to resist the romance of stone. But stone was not always suitable. In certain cases - for example, when spanning especially deep or unsound terrain - iron offered a slender solution that was strong, inexpensive and lightweight.
Most of Britain’s iron viaducts have now been demolished, with many of the more impressive examples unfortunate victims of Dr Beeching’s cuts. This is a profound shame because, drawing words from William Humber’s 1857 treatise on cast and wrought iron railway bridges and viaducts: these “light and elegant structures … may well rank with some of the most important engineering wonders of the day”.
The rarity of iron viaducts across 21st century Britain makes the work of those trying to save what is left vital.
In greatest need of saving is Bennerley Viaduct, a primarily wrought iron example spanning the Erewash Valley between Awesworth in Nottinghamshire and Ilkeston in Derbyshire.
This Grade 2*-listed structure appears on both Historic England’s Heritage at Risk register and in the current iteration (2020) of the World Monuments Fund’s World Monuments Watch, which “seeks to discover, spotlight and take action on behalf of heritage places facing challenges or presenting opportunities of direct relevance to our global society”.
Plans to restore this national treasure and open it up to the community as a public walkway were stemmed by the current pandemic. As we wait for Bennerley’s restoration work to take off in earnest, now is the opportunity to consider why the structure is worth preserving.
Alongside Bennerley, I advance an argument here for the legacy of iron in Britain’s railway viaducts (wrought or otherwise), with special emphasis on the giants of the age - masterpieces of economy and ingenuity that probably should have been saved instead of scrapped. Bennerley has the distinction of being
Britain’s lastsurviving, almost-unaltered, wrought iron viaduct. Another significant structure is the Meldon Viaduct, a Scheduled Monument and now part of a popular walking and cycling route, giving us a glimpse of what could be achieved with Bennerley.
For those iron viaducts lost to us (and there are many), I have selectively chosen to highlight Staithes, Belah and Crumlin, all of which were slender but strengthened through wrought iron.
A number of honourable mentions are also included, and I indulge a detour via James Brunlees’ low-and-long river viaducts.
The failings of cast iron in railway bridgebuilding became common knowledge - tragically, more than two decades after Humber published his treatise - with the Tay Bridge disaster of 1879.
The Tay disaster shaped modern bridge building, and its lessons are important to the history of Britain’s iron viaducts. But we should remember that many grand iron examples stood true, some for more than a century, with a slender beauty and surprising strength.
Bennerley (1878)
Bennerley was initially planned in stone, but the need to withstand subsidence from nearby coal mining meant a wrought iron design won out in the end.
The benefits of iron over stone to combat instabilities of the ground and onslaughts from the natural elements were recognised as early as the 18th century by the great Thomas Telford, who marvelled at the survival of the ‘Iron Bridge’ (a structure that today is part of a UNESCO World Heritage Site) during the flood of 1795, then adopted it himself.
Bennerley was constructed toward the twilight of iron’s use, in 1878, as part of the Derbyshire & Staffordshire Extension on the Great Northern Railway (GNR). It was designed by Richard Johnson, the GNR’s
Chief Civil Engineer, and is 1,452 feet long with the track rising more than 60 feet.
Dowery Dell Viaduct on the Halesowen branch of the Midland Railway is an honourable mention here. It was built around the same time as Bennerley, also with a lattice girder supported on trestles design. We lost it in the 1960s.
Johnson constructed a number of other notable viaducts and bridges along the extension, which Beeching closed in 1964.
Johnson’s other bridges included the spectacular 43-span, 1,716-foot Giltbrook Viaduct (a brick example, two spans of which were converted into dwellings and later acted as air raid shelters) and two bridges in Derby - the wrought iron tied-arch Derwent Bridge and the cast-iron-with-stone-abutments Friar Gate Bridge in the city centre (actually two bridges, which carried four tracks and formed part of the approach to the now-lost Derby Friargate railway station).
In a surprising reversal of the generally far-better-faring fortunes of brick and stone structures along closed lines, it was Johnson’s iron creations that prevailed - in fact, all three of those mentioned, although Friar Gate joins Bennerley as a structure at risk.
Giltbrook’s end came in 1973 when, inexplicably, this culturally significant redbrick beauty was demolished to make way for the A610.
After years of disuse and threats of demolition, in 2001 Bennerley came into the ownership of Railway Paths, a conservation group that has been responsible for the restoration and bringing back into use of key pieces of railway heritage as cycle and walking pathways.
Groundswell to save the monument continued through the pandemic, with news in November 2020 that the site had received a lifeline grant of £165,000 for essential repairs to its parapet walls and eastern abutment. This funding has also safeguarded a large-scale restart of restoration, when possible.
Bennerley would likely not have survived without the efforts of passionate conservationists, who have been combating plans to dismantle it since the 1970s. Yet it is important to note that Bennerley also protected itself through the strength of its materials.
It remained in use for freight traffic until 1968, whereafter it escaped the scrapyard on account of the difficulty that dismantling its wrought-iron structure posed using conventional metal-cutting equipment.
The strength of wrought iron is at the core of what makes Bennerley significant, as we discover on our survey, starting with two other structures that made primary use of it.
Meldon (1874)
Meldon Viaduct in Devon is the only other surviving wrought iron viaduct in Britain.
It consists of a wrought iron truss girder supported on wrought iron piers and can be enjoyed today along the Granite Way - an 11-mile multi-use trail between Okehampton and Lydford at the north western edge of Dartmoor National Park.
It was completed as part of the London & South Western Railway (L&SWR) line from Exeter to Plymouth, and was erected to cross the deep valley of the West Okement River. It is approximately 540 feet long with its tallest pier reaching around 120 feet.
Meldon’s significance is slighter than that of Bennerley’s, given that it is in fact two viaducts tied together. The first was completed in 1874 using riveted wrought iron piers, while the second dates from 1879, when steel was employed in place of iron, with further structural alterations to follow.
It was designed by W R Galbraith, also responsible for the Grade 2-listed L&SWR wrought iron lattice girder Kew Railway
Bridge (still in service today, carrying the North London and District lines) and the nowlost, four-arched West Meon Viaduct on the Meon Valley Railway line (another example of iron used in place of stone).
Staithes, together with its sister viaducts, is our final wrought iron focus.
Staithes (1875, opened 1883)
Staithes Viaduct was the crowning achievement of the Whitby, Redcar & Middlesbrough Union Railway’s stunning Whitby to Loftus line, which hugged the coast at the north east of what is today the North York Moors National Park.
Although the line ran for little more than 16 miles, Staithes was just one of five iron viaducts built to string a single line over a number of deep ravines that varied in width from 300 to 1,000 feet.
Staithes was the largest and most northerly of the five, its piers rising as high as 200 feet in places. The other four viaducts were all in close proximity between Whitby and Sandsend (they were, from Whitby: Upgang, Newholm, Eastrow and Sandsend).
Again, Staithes was not in the same class as Bennerley, having been composed of cast iron as well. But it was strikingly slender and made
novel use of wrought iron in its tubular piers, which were filled with concrete.
Filling iron piers with concrete was novel for the time and gave the viaducts the strength needed to stretch out in iron strides of 30 and 60 feet (Upgang and Eastrow were particular demonstrations of these wider spans).
The viaducts’ designer was John Dixon, whose clashes with his financers were legendary. And while I find the structures beautiful, his primary achievement here was spanning difficult terrain on a slight budget.
“Mr Dixon claims for his invention the merit of being the cheapest form of pier yet introduced, where the height is great and other conditions favourable,” Edward Moss Hutchinson writes in his 1879 history of wrought iron bridge-building.
Obsessions with fiscal economy are important to the history of iron viaducts, in so far as they often necessitated the use of cast iron as well. Thomas Bouch, probably the best-known fiscally conservative engineer of his day, found this when one of his largely cast-iron goliaths collapsed during a storm in December 1879, taking with it a passenger train and all souls on board into the Tay.
It was a disaster that changed how rail bridges and viaducts were built thereafter, and led to alterations on other structures (Staithes, for instance, which delayed its opening). In fact, it helped bring about the end of the age of our slender iron structures altogether.
Casting a long shadow
Rapid expansion of Britain’s transport network during the ‘railway mania’ of the 19th century meant that the testing of engineering principles often played catch-up to the ambitions of progress.
This was most evident in the mid- to advancing-years of the century, when building bridges and viaducts to span some of Britain’s more troubling topographies. In true Victorian bold-as-brass fashion, passengers often travelled across structures built to span ravines and valleys and bodies of fast-moving water, even as debates rolled on into the safety and suitability of materials used.
Discussion around the suitability of cast iron for railway bridge-building is the best example of this. The breaking point almost derailed the career of Robert Stephenson, in the 1847 Dee Bridge disaster, before he could pioneer (with William Fairbairn) the triumph of the wrought iron tubular system, at Conwy and across the Menai Straits.
Wrought iron is essentially iron that has been worked so that its carbon content is radically reduced. For the purposes of rail bridge-building in the 19th century, this proved revolutionary, and highly advantageous over the dangerously brittle properties of cast iron.
Wrought iron helped curb cast iron’s troubles-in-tension and was championed in early usage by greats such as Isambard
Kingdom Brunel, who made use of riveted wrought iron in his 1838 SS Great Britain, and then ran with the material in his bridges.
The consummate visionary, Brunel learnt early (from an 1847 fire on his Great Western Railway’s Hanwell Bridge) that cast iron should be used sparingly and treated with utmost suspicion by the engineering community. He told anyone who would listen - and many who didn’t.
In a letter dated March 13 1848 and addressed to a commission established to investigate the feasibility of iron in railway structures, Brunel wrote plainly that cast iron is “a friable, treacherous and uncertain material” of which “castings of a limited size only can be safely depended upon”.
Wrought iron, he continued, is “comparatively trustworthy, and by riveting, or welding, there is no limit to the size of the parts to be used”.
Brunel spoke on this subject and on many others (his atmospheric principle was a notable exception) with an almost prophetic confidence - in this case in the catastrophic flaws of cast iron, which he believed should not in any regard be depended on as a strengthening device in the carrying of railway loads.
But not all engineers shared Brunel’s distrust of cast iron. And for many - engineers and financers alike, especially earlier in the century - it was a question of cost.
“I never use cast iron if I can help it, but in some cases, it is necessary,” Brunel writes in a letter addressed to the Directors of the GWR, dated April 18 1849.
And when Bouch was constructing viaducts in cast and wrought iron during the 1860s, for instance, contemporary sources quote wrought iron as twice the price per ton.
It is no coincidence that the wrought iron viaducts surveyed in the first part of this story were all products of the 1870s, as technology drove down the price and understandings of the benefits increased.
As Fairbairn wrote at the start of that decade, via wrought iron we have witnessed “the wide and universal extension of a principle now recognised as one of the most important to the advancement and extension of the railway system”.
Bennerley, built over 1876-77 and opened in 1878, stands as testament to the advancement of this principle. It is ironic, therefore, that Bennerley’s triumph should come with an overall decline in the use of iron for immense railway structures.
The cast iron debate was put to rest in spectacular fashion with the structural failure of Bouch’s Tay Bridge, which also ushered in the adoption of an alternative to iron - steel.
The story of steel’s success is written large in the landscape south from the Tay, where Bouch had even made a start on what he had hoped would be the pinnacle of his career.
Of course, this is John Fowler’s and Benjamin Baker’s Forth Bridge - a UNESCO World Heritage Site that through its mass cross-bracing of steel showed strength, fought fear, and restored public confidence in engineers’ abilities to bridge the impossible.
Iron’s viaduct legacy
Bouch’s Tay Bridge has always fascinated me. Woefully inadequate to withstand the conditions where it was built, and blind to the evidence and testimony of established engineering, its collapse was quickened by profound negligence (and reckless arrogance) on his part, as came out in the official inquiry.
But still, at the time of its opening, it was celebrated as the embodiment of engineering magic - making the impossible possible through a structure that was both light and elegant.
In an age of over-engineering, nostalgised today as ‘built-to-last’, the concept of the Tay - as broken as it was, but with its economy and slender grace - was a sight to behold. Queen Victoria even bestowed Bouch a knighthood after travelling over it.
And controversial as this is, with acknowledgement for the pain caused by the tragedy, visually the bridge did embody an essence of what was remarkable about the use of iron to raise rail in a streamlined fashion.
Plus, while I accept that the contribution of Tay Bridge to what Fairbairn terms the “useful arts” is only useful in so far as what our engineers learnt from it, there were other slender iron structures whose usefulness stood strong throughout their service.
In successful examples, cast iron was often used for the piers, while wrought iron was employed for the superstructure (in the girders) as well as in strengthening the structure overall. (Stone piers were also often used, with iron girders - as was the case with the Kilton Viaduct, since buried in shale.)
Before drawing out a few elegant and highin-the-sky examples that successfully mixed cast with wrought iron, it would be remiss not to at least include one engineer who built iron viaducts in a different fashion - low and long.
Leven & Kent (1857) and Solway (1869)
James Brunlees (also famous for his pleasure piers) built low and long iron viaducts - for example, his 1857 Leven and Kent Viaducts, built for the Ulverstone & Lancaster Railway to cross tidal estuaries south of the Lake Distinct.
Leven and Kent were near-identical at 1,563 and 1,566 feet, and originally composed of 395-438 and 406-368 tons of wrought to cast iron respectively.
They were also typical of each other, as Brunlees writes in a letter to the Institution of Civil Engineers (dated April 20 1858) - “so similar, in situation, design and mode of construction” that a plan he nominates of the Leven,“may be taken to represent both structures”.
Leven’s height to the rails was just 26 feet above low water, with Kent even less (23 feet). These examples met the common principle for water-based viaducts, namely as running low and long with short spans.
It was a sound principle - one that, as Brunlees writes, renders a structure “so steady, under the trains, that its position is not apparent in passing over”.
His best-known viaduct was built for the Solway Junction Railway, crossing the Solway Firth at the English-Scottish border.
Solway opened in 1869 as the longest bridging structure in Britain ( before the Tay), stretching around 5,820 feet, using 193 spans and combining cast and wrought iron.
It suffered considerable damage from ice floes in the 1875/76 winter, and then again in 1881, with the latter leading to a Board of Trade inquiry after 45 of its piers were destroyed.
The inquiry emphasised the shortcomings of the viaduct’s cast-iron columns in withstanding the shock of the ice.
Leven and Kent survive and are in service today, although their cast iron columns have been encased with brickwork and concrete. Solway’s iron suffered continual deterioration and the structure was declared unsafe and closed in 1915, and then demolished in 1934-35.
To conclude, I have selected two structures - one from each of the decades preceding 1870. At a time when, in Brunel’s words, cast iron was often necessary, these iron giants were economical and strong, but also light and elegant. Our first example is Bouch’s greatest success.
Belah (1861)
For me, the most extraordinary aspect of the inquiry into the Tay disaster comes in the final 1880 report, when the bridge is compared with Bouch’s Belah (also Beelah) Viaduct.
Belah was erected in iron in 1861 to carry the South Durham & Lancashire Railway (SD&LR) across a mountain gorge in Westmoreland, about four miles from the town of Brough.
The inquiry cites William Humber to set out the various strengths of Bouch’s 1,000foot viaduct, which rose 195 feet at its highest point.
Humber describes Belah as one of the lightest and cheapest of its kind ever erected. It was also strong, was constructed in less than four months without a single accident or injury, was deemed safe by the Board of Trade on first inspection, and stood for more than 100 years until being dismantled in the 1960s, after Beeching cut it from service.
Belah had 15 piers with 60-foot spans and an elaborate series of strengthening elements, chief of which were the use of horizontal and vertical wrought-iron bracings that, according to Humber, when “keyed up, are nearly as rigid as though they were one solid piece”.
In the inquiry, the investigators devote critical attention to Bouch’s poor choice of cast iron lugs as supports on the Tay Bridge, together with its far longer, less-supported spans.
“The only conclusion to which we can come is either that the former [Belah] was extravagantly strong, or the latter [Tay] inordinately weak,” they write.
The Tay Bridge was, in the investigators’ assessment, “badly designed, badly constructed, and badly maintained”, with inherent defects in its structure that “must sooner or later have brought it down”.
Bouch’s obsession with economy also came into play in undermining his Tay design - crucially a decision to deviate from some of the wrought iron elements that gave Belah its strength, because (in his startling revelation to William Henry Barlow, who went on to design the replacement bridge acros the Firth of Tay, constructed of wrought iron and steel) these elements were “so much more expensive, this was a saving of money”.
Built in the same year as Belah, also for the SD&LR and to a similar design (with crossbraced wrought-iron beams and tie bars), Bouch’s Deepdale Viaduct is an honourable mention. It featured a curve and 11 spans across Deepdale Beck. It served for more than 100 years, until the line was closed in 1962, and was demolished soon after.
Crumlin (1857)
Charles Liddell’s Crumlin Viaduct was an even better-known and widely celebrated iron giant.
Around a mile from Pontypool on the Newport, Abergavenny & Hereford Railway, it used 1,325 tons of wrought iron to 1,275 tons of cast iron, with its track running on eight slender piers.
As one report on the opening of Crumlin reads, it “stretches across a mountain gorge upwards of 230 feet deep, thus connecting two mountain tops together by means of a structure of singular grace and elegance, and in appearance so light as to make us think it impossible that a railway train could cross it”.
Iron may not have enjoyed the same staying power as stone when it comes to Britain’s viaducts, but that is not to say that its story is any less significant. In fact, these structures often rose at scales and with spans scarcely set in stone.
In archival photographs, these lost structures appear almost futuristic (even today) in the way they carried trains across deep ravines on slender, balanced combinations of wrought and cast iron.
Bennerley celebrated the strength of wrought iron riveted together to create slender-yet-strong, expansive-but-lightweight, railway viaducts. It is a lonely survivor from the age of steam that must prevail as a matter of great urgency, and as a living reminder of the iron giants that have now almost entirely disappeared from Britain’s landscape.