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An Iron Bridge

An Iron Bridge

Brian Spencer visits one of the industrial revolution’s longest lasting major relics

Gouged out by the last ice age over 15,000 years ago, in the Industrial Revolution the Severn Gorge became a convenient means of moving coal and iron and general commerce, downstream to the burgeoning industrial areas surrounding the river estuary.  Later on and with the expansion of trade, especially when the skills and techniques of forging raw iron grew locally, the industry expanding from simply digging the stuff out of the ground and letting someone else mould it into finished goods.

Coal and limestone had been exploited since the Middle Ages, with iron founding and moulding following during Henry VIII’s reign.  In the early eighteenth century, the Quaker ironmaster, Abraham Darby 1st found ways of increasing the efficiency of iron moulding, allowing the production of everyday objects at easily afforded prices.

The earliest form of iron moulding which used charcoal as a means of heat, was soon overtaken by another new invention.  This was brought about by using coke derived as a by-product left over from the production of coal gas in airtight kilns. Oddly enough, the area where this raw material came from, was called Coalbrookdale, the old name of the district which still covers the scattering of small hamlets along both sides of the Severn Gorge.  Small iron foundries as well as coal and ironstone mines expanded to meet the need for the raw material.

In order to cope with this demand, fleets of sailing barges moved both raw materials and finished goods, up and down the Severn.  By 1758 around 400 vessels daily were trading along the river between Gloucester and Welshpool, and by the end of the century, this number had doubled.  As a result, traffic on the river was getting out of hand, especially during winter when the river often flooded.  By then roads were steadily improving, but only one bridge of any use to the burgeoning industrial area was two miles upstream.  Ideally a bridge at Coalbrookdale would link the two banks and the proposal to build a new bridge was awarded to Abraham Darby 3rd, the youngest member of the iron family.  Linking both banks of the Severn meant that scattered hamlets and a system of narrow lanes, could be linked into one thriving industrial unit.

A company of trustees headed by Abraham Darby 3rd approached the government asking for permission to build a bridge across the Severn at what they considered was its busiest point.  M.Ps. realising that this was likely to be a profitable exercise were quickly in favour of the scheme and as a result, the Act of Parliament authorising the building of a bridge was quickly passed and the scene was set to design a suitable means of crossing the gorge at one of its narrowest points.  It only left a handful of unanswered questions – what was the bridge’s design, and by whom, and what was it to be made from?

In 1773 the question was answered by the trustees asking John Farnolls Pritchard of Shrewsbury to act as architect for the new bridge.  He was a trained joiner, turned architect and his initial thoughts, hardly surprisingly, were  to build a wooden bridge, in fact his eventual design, although cast iron, is built as though it is in fact, made from timber.  He was probably only persuaded to use cast iron because it was fashionable, and chosen by the local ironmaster and entrepreneur ‘Iron Mad’ John Wilkinson.  Although this was the first iron bridge Pritchard had designed, he had already designed several wooden bridges and specialised in the restoration and modernisation of grand houses.  He produced his first design, a single arched structure that avoided the need for a central pier which allowed shipping to pass beneath the bridge in safety.  The only snag was that Pritchard wanted to build the single arch in stone, or timber!  

Work began on erecting the bridge in November 1779, in cast iron. Strong stone pillars held the sideways pressure of a fully loaded bridge made from linked iron arches, admittedly keeping to Pritchard’s love of timber, following joinery techniques in its design down to their interconnected joints such as mortice and tenon without the need of some form of the little known process of welding. 

Pritchard died soon after work on the bridge commenced, so never lived to see the result of his compromise design of cast iron made to look like timber.  Having won his case for the use of cast iron, Abraham Darby was magnanimous towards Pritchard, even after the latter’s death.  In 1779, Darby was so convinced that the bridge would be a success that he gave £40 to Pritchard’s brother, in payment for drawings and scale models of the bridge, although the final design and construction of the bridge incorporated several modifications to the original design.  

What became known as Darby’s Bridge was the first in the known world to use load bearing cast iron as its main structure.  Acknowledged almost as a new Wonder of the World, artists and writers waxed lyrically about it and spies came from all over the world in order to capture details of its design, a design that was soon to be spotted in different versions crossing gaps and waterways around the developing world.

Basically the bridge was a series of five semi-circular cast iron load bearing arches linked by cast iron copies of timber joints, made by using joinery techniques.  Sideways pressure was held by stone pillars that also allowed approach roads to rise high enough to cross the bridge’s load bearing summit arch.  The joints being copies of those made from timber, such as dovetails and mortices and tenon, allowed the bridge a degree of flexing, that in turn allowed it to withstand the pressure of flood water even into the twenty-first century.

Bridge building then as now was an expensive undertaking.  Abraham Darby’s Iron Bridge when it was officially opened on New Year’s Day 1781 having cost Abraham Darby and his Quaker friends, many of whom having faith in the eventual success of the venture, took out mortgages on their homes.  The final cost of the bridge came to over £6000 – £1,315,228.80 in today’s terms.  Most of the original documents still exist, and they give an insight into the careful planning that went on right up to the day when the first pedestrians paid an old halfpenny and carriages drawn by six horses, crossed this marvel having paid the toll keeper two old shillings.  A detailed list of costs is also available in the old toll house where a small museum tells the story of this iron marvel.  When HRH the Prince of Wales (as he was then) crossed the bridge in 1979, commemorating its two hundred years anniversary, he paid a specially produced halfpenny.


Houses and pubs in Ironbridge cling precariously to the hillside high above the Severn Gorge.  Linked by their 250 year-old bridge, this is a unique link with the time when the night sky blazed bright red with the smoke and flames of long disused foundries.  Small boats and one-man coracles still ply along the river, the latter used during the spring salmon run in order to catch the small quantity of this excellent game fish still legally available.

There are a number of small museums dotted up and down the gorge, on either side of the iron bridge.  These range from examples of the famous Coalbrookdale tiles, to restored industrial houses and small towns such as Blists Hill further along the valley.  Blists Hill is a small town where restored shops, houses and pubs seem to still fit into the 1920s environment above a collection of old factory premises that evoke the industries of not so long ago.  There are a couple of still viable small coal mines, a short length of canal, all are served by a traditional bank where it is possible to ‘buy’ old pennies (at today’s spoiler rate that ranges from 40p for one old penny, to £2.40 for six old pence). 

These grossly inflated pennies can be spent in the New Inn, a typical spit and sawdust street corner public house.  Permanently overseen by a typical friendly village bobby on his trusty old bicycle, the pub, now a thing of the past, still sells Bank’s Ales, a traditional Birmingham Brewery; but probably the best feature from past times is the chip shop, where everything is still fried in proper fat, not vegetable oil, giving the fish and chips their unique crispness.  Anyone without the energy to wander round the town can avoid the exercise by taking a ride in the open horse drawn carriages trotting up and down this quaintly evocative old industrial town.


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