The Iron Bridge
Overview
 
The Iron Bridge crosses the River Severn
River Severn
The River Severn is the longest river in Great Britain, at about , but the second longest on the British Isles, behind the River Shannon. It rises at an altitude of on Plynlimon, Ceredigion near Llanidloes, Powys, in the Cambrian Mountains of mid Wales...

 at the Ironbridge Gorge
Ironbridge Gorge
The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England.Originally called the Severn Gorge, the gorge now takes its name from its famous Iron Bridge, the first iron bridge of its kind in the world, and a monument to the industry that began there...

, by the village of Ironbridge
Ironbridge
Ironbridge is a settlement on the River Severn, at the heart of the Ironbridge Gorge, in Shropshire, England. It lies in the civil parish of The Gorge, in the borough of Telford and Wrekin...

, in Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It was the first arch bridge
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...

 in the world to be made out of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

, a material which was previously far too expensive to use for large structures. However, a new blast furnace
Blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...

 nearby lowered the cost and so encouraged local engineers and architects to solve a long-standing problem of a crossing over the river.
In the early eighteenth century, the only way to cross the Severn Gorge
Ironbridge Gorge
The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England.Originally called the Severn Gorge, the gorge now takes its name from its famous Iron Bridge, the first iron bridge of its kind in the world, and a monument to the industry that began there...

 was by ferry
Ferry
A ferry is a form of transportation, usually a boat, but sometimes a ship, used to carry primarily passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate on regular, frequent, return services...

.
Encyclopedia
The Iron Bridge crosses the River Severn
River Severn
The River Severn is the longest river in Great Britain, at about , but the second longest on the British Isles, behind the River Shannon. It rises at an altitude of on Plynlimon, Ceredigion near Llanidloes, Powys, in the Cambrian Mountains of mid Wales...

 at the Ironbridge Gorge
Ironbridge Gorge
The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England.Originally called the Severn Gorge, the gorge now takes its name from its famous Iron Bridge, the first iron bridge of its kind in the world, and a monument to the industry that began there...

, by the village of Ironbridge
Ironbridge
Ironbridge is a settlement on the River Severn, at the heart of the Ironbridge Gorge, in Shropshire, England. It lies in the civil parish of The Gorge, in the borough of Telford and Wrekin...

, in Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It was the first arch bridge
Arch bridge
An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side...

 in the world to be made out of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

, a material which was previously far too expensive to use for large structures. However, a new blast furnace
Blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...

 nearby lowered the cost and so encouraged local engineers and architects to solve a long-standing problem of a crossing over the river.

Construction

In the early eighteenth century, the only way to cross the Severn Gorge
Ironbridge Gorge
The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England.Originally called the Severn Gorge, the gorge now takes its name from its famous Iron Bridge, the first iron bridge of its kind in the world, and a monument to the industry that began there...

 was by ferry
Ferry
A ferry is a form of transportation, usually a boat, but sometimes a ship, used to carry primarily passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate on regular, frequent, return services...

. However, the industries
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...

 that were growing in the area of Coalbrookdale
Coalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. This is where iron ore was first smelted by Abraham Darby using easily mined "coking coal". The coal was drawn from drift mines in the sides...

 and Broseley
Broseley
Broseley is a small town in Shropshire, England with a population of 4,912 . The River Severn flows to the north and east of the town. Broseley has a town council and is part of the area controlled by Shropshire Council. The first iron bridge in the world was built in 1779 to link Broseley with...

 needed a more reliable crossing.

In 1773, Thomas Farnolls Pritchard
Thomas Farnolls Pritchard
Thomas Farnolls Pritchard was an English architect and interior decorator who is best remembered for his design of the first iron bridge in the world....

 wrote to a local ironmaster
Ironmaster
An ironmaster is the manager – and usually owner – of a forge or blast furnace for the processing of iron. It is a term mainly associated with the period of the Industrial Revolution, especially in Great Britain....

, John Wilkinson
John Wilkinson (industrialist)
John "Iron-Mad" Wilkinson was an English industrialist who pioneered the use and manufacture of cast iron and cast-iron goods in the Industrial Revolution.-Early life:...

 of Broseley
Broseley
Broseley is a small town in Shropshire, England with a population of 4,912 . The River Severn flows to the north and east of the town. Broseley has a town council and is part of the area controlled by Shropshire Council. The first iron bridge in the world was built in 1779 to link Broseley with...

, to suggest building a bridge out of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

. By 1775, Pritchard had finalised the plans, but he died in December 1777, only a month after work had begun.

Abraham Darby III
Abraham Darby III
Abraham Darby III was an English ironmaster and Quaker. He was the third Abraham Darby in three generations of an English Quaker family that played a role in the Industrial Revolution....

, who was the grandson of the first foundry owner and an ironmaster working at Coalbrookdale
Coalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. This is where iron ore was first smelted by Abraham Darby using easily mined "coking coal". The coal was drawn from drift mines in the sides...

 in the gorge, was commissioned to cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

 and build the bridge. The iron for the new bridge was cast at his foundry.
Shares
Share (finance)
A joint stock company divides its capital into units of equal denomination. Each unit is called a share. These units are offered for sale to raise capital. This is termed as issuing shares. A person who buys share/shares of the company is called a shareholder, and by acquiring share or shares in...

 were issued to raise the £3,200 required, and Darby agreed to fund any overspend. Although it had been predicted that 300 ton
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...

s of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 would be needed (costing £7 a ton), in the end 379 tons were used, costing Darby and his company nearly £3,000. There would be many other costs to bear (masonry abutments, assembly, etc.), so that the project was far more expensive than first envisaged. Darby bore most of the cost over-run, and got into debt for the rest of his short life.

Being the first of its sort, the construction had no precedent; the method chosen to create the structure was therefore based on carpentry
Carpentry
A carpenter is a skilled craftsperson who works with timber to construct, install and maintain buildings, furniture, and other objects. The work, known as carpentry, may involve manual labor and work outdoors....

. Each member of the frame was cast separately, and fastenings followed those used in woodworking, such as the mortise and tenon
Mortise and tenon
The mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, mainly when the adjoining pieces connect at an angle of 90°. In its basic form it is both simple and strong. Although there are many joint variations, the basic mortise and tenon...

 and blind dovetail joints. Bolts were used to fasten the half-ribs together at the crown of the arch. Very large parts were needed to create a structure to span 100 feet rising to 60 feet above the river. The largest parts were the half-ribs, each about 70 ft long and weighing 5.25 tons. The bridge comprises more than 800 castings of 12 basic types.

The bridge was raised in the summer of 1779, and it was opened on New Year's Day 1781. In 2001, the BBC screened a documentary in which a half-sized model of the bridge was built to test recent research over the construction. Instead of large timber towers, a pair of uprights with a crosspiece was used to erect each of the ribs in sequence. The abutments were built afterwards.

Repairs

Just a few years after the construction of the bridge, cracks appeared in the masonry abutments, partly caused by ground movement. Some of the present-day cracks in the cast iron may date from this time, although others are probably casting cracks from defects such as blow holes. Some cracks were pinned with wrought iron
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

 straps, but others have been left free. By 1802, the southern stone abutment had to be demolished and replaced with temporary wooden arches before eventually being replaced by iron arches. However, many of the cracks visible in the bridge today have been left untouched. The bridge was over-designed and subsequent bridges, such as those built by Thomas Telford
Thomas Telford
Thomas Telford FRS, FRSE was a Scottish civil engineer, architect and stonemason, and a noted road, bridge and canal builder.-Early career:...

, used much less cast iron. For example, his cast iron arch bridge at Buildwas
Buildwas
Buildwas is a village and civil parish in Shropshire, England, on the north bank of the River Severn at . It lies on the B4380 road to Atcham. The Royal Mail postcodes begin TF6 and TF8Buildwas Primary School is situated on the Buildwas bank road...

, upstream from Ironbridge, used less than half the weight for a greater span (130 foot span, 170 tons of cast iron). However, it suffered similar problems of abutment movement and was replaced in 1902.

The cast iron bridge at Coalport
Coalport
Coalport is a village in Shropshire, now part of the new town of Telford. It is located on the River Severn at , a mile downstream of Ironbridge...

 downstream, built in 1818, is much more impressive because of its lean, streamlined design, and the higher quality of the cast iron arches. Thus it still carries vehicular traffic, albeit as a single carriageway. It has about half the weight of cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 as the original Ironbridge, and is longer than the earlier iron structure. It was renovated in 2004 including replacement of the cast iron pavement by lighter equivalents.
More information about how the bridge was built came from the discovery in 1997 of a small watercolour by Elias Martin in a Stockholm museum. This showed the bridge under construction in 1779.

In 1972, a programme of major repairs took place on the foundations of the bridge. It involved creating a ferro-concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

 counter-arch
Counter-arch
A counter-arch is built adjacent to another arch to oppose its forces or help stabilize it....

 under the river.
In 1999-2000, the bridge was renovated again, with replacement of the cast iron road plates with steel plates, and a lightweight top surface.

These renovations, together with recent research, revealed more about the building process and the manufacture of the cast iron parts. While the smaller parts were cast using wooden patterns, the large ribs were cast into excavated moulds in the casting sand. It is now known that 70 per cent of the components were made individually to fit, and as a result each is slightly different from the others. Darby’s workers employed woodworking joints – mortises and tenons, dovetails and wedges – and adapted them to the different properties of cast iron. English Heritage, together with the Ironbridge Gorge Museums Trust, carried out a full archaeological survey, record and analysis of the bridge in 1999–2000. A half-size replica of the main section of the bridge was built in 2001 as part of the research for the BBC Timewatch programme which was shown in 2002.

Ironbridge settlement

The Iron Bridge became an 18th century tourist attraction and the settlement of Ironbridge
Ironbridge
Ironbridge is a settlement on the River Severn, at the heart of the Ironbridge Gorge, in Shropshire, England. It lies in the civil parish of The Gorge, in the borough of Telford and Wrekin...

 grew up beside it. Although described by many as a town, the market is that of nearby Madeley
Madeley
-People:* Anna Madeley , actress* Chloe Madeley , television presenter* Darrin Madeley , ice hockey player* Keith Madeley, businessman* Paul Madeley , footballer* Richard Madeley , television presenter...

, and today Ironbridge falls within the parish of The Gorge
Ironbridge Gorge
The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England.Originally called the Severn Gorge, the gorge now takes its name from its famous Iron Bridge, the first iron bridge of its kind in the world, and a monument to the industry that began there...

. Today, Ironbridge is one of the 21 British icons.

Iron Bridge Tollhouse

The bridge's original toll house
Toll house
A tollhouse or toll house is a building with accommodation for a toll collector, beside a tollgate on a toll road or canal. Many tollhouses were built by turnpike trusts in England, Wales and Scotland during the 18th and early 19th centuries...

 is open on weekends during the summer. Exhibits focus on the history of the bridge and its construction. It has now closed down, however.

The present day

Iron Bridge was finally barred to vehicular traffic in 1934 when it was designated as an ancient monument, but tolls
Toll bridge
A toll bridge is a bridge over which traffic may pass upon payment of a toll, or fee.- History :The practice of collecting tolls on bridges probably harks back to the days of ferry crossings where people paid a fee to be ferried across stretches of water. As boats became impractical to carry large...

 for pedestrians still were collected until 1950, when ownership of the bridge was transferred to Shropshire County Council. It now belongs to Telford and Wrekin
Telford and Wrekin
Telford and Wrekin is a unitary district with borough status in the West Midlands region of England. For Eurostat purposes it is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. The district was created in 1974 as The...

 Borough Council.

The bridge, the adjacent settlement and the natural gorge together form a popular tourist destination, and form part of the UNESCO
UNESCO
The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations...

 Ironbridge Gorge World Heritage Site
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...

. The Iron Bridge is a Grade I listed building and a Scheduled Ancient Monument.

The bridge is a waypoint on the South Telford Heritage Trail
South Telford Heritage Trail
The South Telford Heritage Trail is a circular, waymarked walking route that passes by forty-nine heritage sites in the English town of Telford.-Total Distance:The approximate distance of the trail is 12.2 miles...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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