Pontcysyllte Aqueduct
Encyclopedia
The Pontcysyllte Aqueduct (ˌpɔntkəˈsəɬtɛ, full name in ) is a navigable aqueduct
that carries the Llangollen Canal
over the valley of the River Dee
in Wrexham in north east Wales
.
Completed in 1805, it is the longest and highest aqueduct in Britain
, a Grade I Listed Building and a World Heritage Site
.
When the bridge was built it linked the villages of Froncysyllte
, at the southern end of the bridge in the Cysyllte township of Llangollen parish (from where it takes its name ), and Trevor
, at the northern end of the bridge in the Trevor Isaf township of Llangollen parish. Both townships were later transferred to Wrexham County Borough following local government reorganisation.
The name is in the Welsh language
and means "Cysyllte Bridge". For most of its existence it was known as ("Bridge of Cysyllte"). Other translations such as "Bridge of the Junction" or "The Bridge that links" are modern, and incorrect, inventions, from the literal English translation of being "junctions" or "links".
and William Jessop
, is 1007 ft (306.9 m) long, 11 ft (3.4 m) wide and 5.25 ft (1.6 m) deep. It consists of a cast iron
trough supported 126 ft (38.4 m) above the river on iron arched ribs carried on nineteen hollow masonry piers (pillars). Each span is 53 ft (16.2 m) wide. Despite considerable public scepticism, Telford was confident the construction method would work: he had previously built at least one cast iron trough aqueduct – the Longdon-on-Tern
aqueduct on the Shrewsbury Canal
, still visible in the middle of a field, though the canal was abandoned years ago. Part of what was originally called the Ellesmere Canal
, it was one of the first major feats of civil engineering
undertaken by Telford, by then a leading civil engineer
, supervised by Jessop, the more experienced canal engineer. The iron was supplied by William Hazledine
from his foundries at Shrewsbury
and nearby Cefn Mawr
. It was opened on 26 November 1805, having taken around ten years to design and build at a total cost of £
47,000. Adjusted for inflation this is equal to £ as of , however a structure of this type would cost more to build today due to other factors that didn't exist in the early 19th century such as higher wages (adjusted for inflation), safety measures, new regulations and taxes, financing fees and so on.
The lime mortar
used lime, water and ox blood. The iron
castings were produced at the nearby Plas Kynaston Foundry, Cefn Mawr, which was built for the purpose. The trough was made from flange
d plates of cast iron, bolted together, with the joints bedded with Welsh flannel
and a mixture of white lead
and iron particles
from boring waste. The plates are not rectangular but shaped as voussoir
s, similar to those of a stone arch. There is no structural significance to this: it is a decorative feature only, following the lines of the stiffening plates (see below) in the castings beneath. The supporting arches, four for each span, are in the form of cast iron ribs, each cast as three voussoirs with external arches cast with an un-pierced web
to give greater strength at the cost of extra weight. Using cast iron in this way, in the same manner as the stone arch it supersedes, makes use of the material's strength in compression. They also give an impression of greater solidity than would be the case were the webs pierced. This impression is enhanced by the arrangement of strips of thicker stiffening incorporated into the castings, arranged in the manner of joints between voussoirs. Cast plates are laid transversely to form the bed of the canal trough. The trough is not fastened to the arches, but lugs
are cast into the plates to fit over the rib arches to prevent movement. It was left for six months with water inside to check it was watertight. A feature of a canal aqueduct, in contrast with a road or railway viaduct, is that the vertical loading stresses are virtually constant. According to Archimedes' principle
, the mass (weight) of a boat and its cargo on the bridge, pushes an equal mass of water off the bridge
The towpath
is mounted above the water in the trough. This arrangement allows the water displaced by the passage of a narrow boat to flow easily around it, enabling relatively free passage. Pedestrians and horses once used for towing, are protected from falling from the aqueduct by railings on the outside edge of the towpath, but the holes in the top flange of the other side of the trough, capable of mounting railings were never used. The trough sides rise only about 6 inches (15.2 cm) above the water level, less than the depth of freeboard of an empty narrow boat, so the helmsman of the boat has no visual protection from the impression of being at the edge of an abyss. The trough of the Cosgrove aqueduct
has a similar structure, although it rests on trestles rather than iron arches. It is also less impressively high.
Every five years the ends of the aqueduct are closed and a plug in one of the highest spans is opened to drain the canal water into the River Dee below, for inspection and maintenance of the trough.
Despite the huge costs of constructing the aqueduct, the canal effectively ends after a short distance on the north side, apart from a feeder canal to Llangollen and the Horseshoe Falls on the River Dee. The terrain northwards appears to have been the main problem in preventing the intended further extension to the north.
World Heritage Site status in 1999. The aqueduct was suggested as a contender in 2005—its 200th anniversary year—and it was formally announced in 2006 that a larger proposal, covering a section of the canal from the aqueduct to Horseshoe Falls would be the United Kingdom's 2008 nomination.
The length of canal from Rhoswiel, Shropshire
to the Horseshoe Falls including the main Pontcysyllte Aqueduct structure as well as the older Chirk Aqueduct
, were visited by assessors from UNESCO during October 2008, to analyse and confirm the site management and authenticity. The aqueduct was inscribed by UNESCO on the World Heritage List on 27 June 2009, alongside previously inscribed sites such as the Taj Mahal
, Great Wall of China
and Stonehenge
.
In March 2010 it was reported that the site had attracted a thriving community of otters
Navigable aqueduct
Navigable aqueducts are bridge structures that carry navigable waterway canals over other rivers, valleys, railways or roads. They are primarily distinguished by their size, carrying a larger cross-section of water than most water-supply aqueducts...
that carries the Llangollen Canal
Llangollen Canal
The Llangollen Canal is a navigable canal crossing the border between England and Wales. The waterway links Llangollen in Denbighshire, north Wales, with Hurleston in south Cheshire, via the town of Ellesmere, Shropshire....
over the valley of the River Dee
River Dee, Wales
The River Dee is a long river in the United Kingdom. It travels through Wales and England and also forms part of the border between the two countries....
in Wrexham in north east Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
.
Completed in 1805, it is the longest and highest aqueduct in Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, a Grade I Listed Building and a 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...
.
When the bridge was built it linked the villages of Froncysyllte
Froncysyllte
Froncysyllte , commonly colloquially known as Fron, is a village in Wrexham county borough, Wales and stands on the banks of the River Dee and the Llangollen Canal...
, at the southern end of the bridge in the Cysyllte township of Llangollen parish (from where it takes its name ), and Trevor
Trevor, Wrexham
Trevor is a village in the county borough of Wrexham in Wales. It is situated in the scenic Vale of Llangollen, on the A539 between Llangollen and Wrexham in the community of Llangollen Rural....
, at the northern end of the bridge in the Trevor Isaf township of Llangollen parish. Both townships were later transferred to Wrexham County Borough following local government reorganisation.
The name is in the Welsh language
Welsh language
Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...
and means "Cysyllte Bridge". For most of its existence it was known as ("Bridge of Cysyllte"). Other translations such as "Bridge of the Junction" or "The Bridge that links" are modern, and incorrect, inventions, from the literal English translation of being "junctions" or "links".
History
The aqueduct, built by Thomas TelfordThomas Telford
Thomas Telford FRS, FRSE was a Scottish civil engineer, architect and stonemason, and a noted road, bridge and canal builder.-Early career:...
and William Jessop
William Jessop
William Jessop was an English civil engineer, best known for his work on canals, harbours and early railways in the late 18th and early 19th centuries.-Early life:...
, is 1007 ft (306.9 m) long, 11 ft (3.4 m) wide and 5.25 ft (1.6 m) deep. It consists of a 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...
trough supported 126 ft (38.4 m) above the river on iron arched ribs carried on nineteen hollow masonry piers (pillars). Each span is 53 ft (16.2 m) wide. Despite considerable public scepticism, Telford was confident the construction method would work: he had previously built at least one cast iron trough aqueduct – the Longdon-on-Tern
Longdon-on-Tern
Longdon-on-Tern is a village in east central Shropshire, England. It is in the unitary district of Telford and Wrekin, and is approximately east of Shrewsbury and north-west of Telford....
aqueduct on the Shrewsbury Canal
Shrewsbury Canal
The Shrewsbury Canal was a canal in Shropshire, England. Authorised in 1793, the main line from Trench to Shrewsbury was fully open by 1797, but it remained isolated from the rest of the canal network until 1835, when the Birmingham and Liverpool Junction Canal built the Newport Branch from...
, still visible in the middle of a field, though the canal was abandoned years ago. Part of what was originally called the Ellesmere Canal
Ellesmere Canal
The Ellesmere Canal was a canal in England and Wales, originally planned to link the Rivers Mersey, Dee, and Severn, by running from Netherpool to Shrewsbury. The canal that was eventually constructed was very different from what was originally envisioned...
, it was one of the first major feats of civil engineering
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
undertaken by Telford, by then a leading civil engineer
Civil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...
, supervised by Jessop, the more experienced canal engineer. The iron was supplied by William Hazledine
William Hazledine
William Hazledine was a pioneering English Ironmaster whose talent for casting structural ironwork helped to realise the designs of engineers such as Thomas Telford and architects including Henry Goodridge and Charles Bage...
from his foundries at Shrewsbury
Shrewsbury
Shrewsbury is the county town of Shropshire, in the West Midlands region of England. Lying on the River Severn, it is a civil parish home to some 70,000 inhabitants, and is the primary settlement and headquarters of Shropshire Council...
and nearby Cefn Mawr
Cefn Mawr
Cefn Mawr is a large village in the community of Cefn within the County Borough of Wrexham, Wales. Its name translates as "great ridge".The community of Cefn comprises the villages of Cefn Mawr, Cefn-bychan , Acrefair, Penybryn, Newbridge, Plasmadoc and Rhosymedre and is situated on the northern...
. It was opened on 26 November 1805, having taken around ten years to design and build at a total cost of £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
47,000. Adjusted for inflation this is equal to £ as of , however a structure of this type would cost more to build today due to other factors that didn't exist in the early 19th century such as higher wages (adjusted for inflation), safety measures, new regulations and taxes, financing fees and so on.
Structure
Lime mortar
Lime mortar is a type of mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, dating back to the 4th century BC and widely used in Ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to Ancient...
used lime, water and ox blood. The 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...
castings were produced at the nearby Plas Kynaston Foundry, Cefn Mawr, which was built for the purpose. The trough was made from flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
d plates of cast iron, bolted together, with the joints bedded with Welsh flannel
Flannel
Flannel is a soft woven fabric, of various fineness. Flannel was originally made from carded wool or worsted yarn, but is now often made from either wool, cotton, or synthetic fibre. Flannel may be brushed to create extra softness or remain unbrushed. The brushing process is a mechanical process...
and a mixture of white lead
Cerussite
Cerussite is a mineral consisting of lead carbonate , and an important ore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruse to the mineral, whilst the present form, cerussite, is due to...
and iron particles
Swarf
Swarf, also known as turnings, chips, or filings, are shavings and chippings of metal — the debris or waste resulting from metalworking operations including milling and grinding. It can usually be recycled, and this is the preferred method of disposal due to the environmental concerns regarding...
from boring waste. The plates are not rectangular but shaped as voussoir
Voussoir
A voussoir is a wedge-shaped element, typically a stone, used in building an arch or vault.Although each unit in an arch or vault is a voussoir, two units are of distinct functional importance: the keystone and the springer. The keystone is the center stone or masonry unit at the apex of an arch. A...
s, similar to those of a stone arch. There is no structural significance to this: it is a decorative feature only, following the lines of the stiffening plates (see below) in the castings beneath. The supporting arches, four for each span, are in the form of cast iron ribs, each cast as three voussoirs with external arches cast with an un-pierced web
I-beam
-beams, also known as H-beams, W-beams , rolled steel joist , or double-T are beams with an - or H-shaped cross-section. The horizontal elements of the "" are flanges, while the vertical element is the web...
to give greater strength at the cost of extra weight. Using cast iron in this way, in the same manner as the stone arch it supersedes, makes use of the material's strength in compression. They also give an impression of greater solidity than would be the case were the webs pierced. This impression is enhanced by the arrangement of strips of thicker stiffening incorporated into the castings, arranged in the manner of joints between voussoirs. Cast plates are laid transversely to form the bed of the canal trough. The trough is not fastened to the arches, but lugs
Lug (knob)
A Lug is a typically flattened protuberance, a knob, or extrusion on the side of a vessel: pottery, jug, glass, vase, etc. They are sometimes found on prehistoric ceramics/stone-vessels such as pots from Ancient Egypt, Hembury ware, claw beakers, and boar spears.A lug may also only be shaped as a...
are cast into the plates to fit over the rib arches to prevent movement. It was left for six months with water inside to check it was watertight. A feature of a canal aqueduct, in contrast with a road or railway viaduct, is that the vertical loading stresses are virtually constant. According to Archimedes' principle
Archimedes' principle
Archimedes' principle relates buoyancy to displacement. It is named after its discoverer, Archimedes of Syracuse.-Principle:Archimedes' treatise On floating bodies, proposition 5, states that...
, the mass (weight) of a boat and its cargo on the bridge, pushes an equal mass of water off the bridge
The towpath
Towpath
A towpath is a road or trail on the bank of a river, canal, or other inland waterway. The purpose of a towpath is to allow a land vehicle, beasts of burden, or a team of human pullers to tow a boat, often a barge...
is mounted above the water in the trough. This arrangement allows the water displaced by the passage of a narrow boat to flow easily around it, enabling relatively free passage. Pedestrians and horses once used for towing, are protected from falling from the aqueduct by railings on the outside edge of the towpath, but the holes in the top flange of the other side of the trough, capable of mounting railings were never used. The trough sides rise only about 6 inches (15.2 cm) above the water level, less than the depth of freeboard of an empty narrow boat, so the helmsman of the boat has no visual protection from the impression of being at the edge of an abyss. The trough of the Cosgrove aqueduct
Cosgrove aqueduct
Cosgrove aqueduct is a navigable cast iron trough aqueduct that carries the Grand Union Canal over the River Great Ouse, on the borders between Buckinghamshire and Northamptonshire at the northwest margin of Milton Keynes in England. The present structure was built in 1811, to replace a previous...
has a similar structure, although it rests on trestles rather than iron arches. It is also less impressively high.
Every five years the ends of the aqueduct are closed and a plug in one of the highest spans is opened to drain the canal water into the River Dee below, for inspection and maintenance of the trough.
Despite the huge costs of constructing the aqueduct, the canal effectively ends after a short distance on the north side, apart from a feeder canal to Llangollen and the Horseshoe Falls on the River Dee. The terrain northwards appears to have been the main problem in preventing the intended further extension to the north.
World Heritage Site
The aqueduct and surrounding lands were submitted to the tentative list of properties being considered for UNESCOUNESCO
The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations...
World Heritage Site status in 1999. The aqueduct was suggested as a contender in 2005—its 200th anniversary year—and it was formally announced in 2006 that a larger proposal, covering a section of the canal from the aqueduct to Horseshoe Falls would be the United Kingdom's 2008 nomination.
The length of canal from Rhoswiel, 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...
to the Horseshoe Falls including the main Pontcysyllte Aqueduct structure as well as the older Chirk Aqueduct
Chirk Aqueduct
Chirk Aqueduct is a high and long navigable aqueduct that carries what is now the Llangollen Canal across the Ceiriog Valley near Chirk, on the England-Wales border....
, were visited by assessors from UNESCO during October 2008, to analyse and confirm the site management and authenticity. The aqueduct was inscribed by UNESCO on the World Heritage List on 27 June 2009, alongside previously inscribed sites such as the Taj Mahal
Taj Mahal
The Taj Mahal is a white Marble mausoleum located in Agra, India. It was built by Mughal emperor Shah Jahan in memory of his third wife, Mumtaz Mahal...
, Great Wall of China
Great Wall of China
The Great Wall of China is a series of stone and earthen fortifications in northern China, built originally to protect the northern borders of the Chinese Empire against intrusions by various nomadic groups...
and Stonehenge
Stonehenge
Stonehenge is a prehistoric monument located in the English county of Wiltshire, about west of Amesbury and north of Salisbury. One of the most famous sites in the world, Stonehenge is composed of a circular setting of large standing stones set within earthworks...
.
In March 2010 it was reported that the site had attracted a thriving community of otters
See also
- Canals of the United KingdomCanals of the United KingdomThe canals of the United Kingdom are a major part of the network of inland waterways in the United Kingdom. They have a colourful history, from use for irrigation and transport, through becoming the focus of the Industrial Revolution, to today's role for recreational boating...
- List of canal aqueducts in Great Britain
- List of bridges in Wales
Further reading
- "Memories of Pontcysyllte" by Amy Douglas and Fiona Collins (2006)
- "Pontcysyllte Aqueduct and Canal Nomination as a World Heritage Site: Nomination Document" (Wrexham County Borough Council and the Royal Commission on the Ancient and Historical Monuments of Wales, 2008)
External links
- 360 Degree panoramic view at BBC Shropshire (Java Applet Required)
- Aerial photo at Windows Live Local
- Wrexham on-line tour: Pontcysyllte Aqueduct
- Construction visualisation video
- Articles on the construction of the Pontcysyllte Aqueduct from the Royal Commission on Ancient and Historical Monuments of Wales
- Management plan for the nomination as a World Heritage Site. Includes detailed description on the scope of the World Heritage site which starts at Rhoswiel and goes through to the Horseshoe Falls