The pontcysyllte aqueduct and canalDocument Transcript
Pontcysyllte Aqueduct and CanalSituated in north-eastern Wales, the 18 kilometre long Pontcysyllte Aqueduct and Canal areremarkable examples of the construction of a human-engineered waterway in a difficultgeographical environment, at the end of the 18th century and the start of the 19th century. Itrequired extensive and boldly conceived civil engineering works. The Pontcysyllte Aqueduct is apioneering masterpiece of engineering and monumental architecture by the famous civilengineer Thomas Telford. It was constructed using metal arches supported by tall, slendermasonry piers. The Pontcysyllte Aqueduct and Canal are early and outstanding examples of theinnovations brought about by the Industrial Revolution in Britain, where they made decisivedevelopment in transport capacities possible. They bear witness to very substantialinternational interchanges and influences in the fields of inland waterways, civil engineering,land-use planning, and the application of iron in structural design.At over 1000 feet long, Pontcysyllte is the longest and highest cast-iron aqueduct in the world.Treasured by British Waterways, it is today a Welsh National Monument and is one of the sevenwonders of the British Inland Waterways System. It is of course still used for its originalpurpose, being crossed by more than a thousand canal boats a year. Moreover, people walkacross it. The footpath, protected on one side by a metal railing, is just about wide enough for awheelchair, but there’s no barrier between the path and the narrow canal trough runningalongside it.The aqueduct helps the Llangollen Canal continue across the valley of the River Dee, inWrexham in north east Wales. Its cast-iron trough is 1,007 feet long, 11 feet wide and 5.25 feetdeep, and accommodates canal boats. It is supported 126 feet above the riverbed by ironarched ribs carried on 19 hollow masonry piers. Each span is 53 feet across.During the aqueducts 10 years of planning and construction, Telford fought past a publicskeptical that his design of cast-iron plates fixed in masonry would work; his experienceworking on another cast-iron trough aqueduct gave him the confidence his plan would succeed.Indeed it has, for 205 years and counting.In Welsh, Pontcysyllte means junction or link bridge, and for most of its existence the aqueductwas known as Pont y Cysyllte. In 2009, it achieved global landmark status when the UnitedNations designated Pontcysyllte Aqueduct a UNESCO World Heritage Site.
Historical DescriptionIn order to link Chester and the Mersey estuary to the Severn and the Midlands canal network,the Ellesmere Canal was conceived in the early 1790s. It was undertaken by a private companyunder the technical supervision of the engineer William Jessop (1745-1814). The constructionof three branches was started from the central point of Ellesmere. The need for water and therich reserves of coal and limestone in the Dee and Ceiriog valleys, in the foothills of the Welshmountains, led to the extension of the project in this direction by a fourth section. The worksbegan in 1795.However, linking the northern side of the Dee to the Ellesmere canals, crossing the RiversCeiriog and Dee, which have very pronounced valleys, presented two major obstacles. From1793 onwards, Jessop worked in collaboration with Thomas Telford (1757-1834) for this branchof the canal. Telford was an outstanding engineer and architect who had a remarkable abilityfor finding new technical solutions to building and civil-engineering problems. He was alreadywell known when he was engaged and had just undertaken the construction of several cast-ironbridges, such as the Longdon aqueduct to cross the Severn. He also proposed a cast-iron bridgeto cross the Thames. In the same region he was also employed to build the road from Londonto Dublin.The aqueduct over the Ceiriog at Chirk was the first structure to be planned, in 1795, by Jessopand Telford. After considerable discussion a stone structure was preferred. Shortly afterwards,when the crossing of the Dee came up for consideration, the conditions were different. Thevalley was wider and deeper, and a conventional aqueduct would therefore have been be verycostly; furthermore, cast-iron bridges were beginning to prove their qualities. The cast-ironbridge solution proposed by Telford was chosen and construction work began under hissupervision. The canal up to Trevor was opened on 26 November 1805. The part which extendsthe canal to Horseshoe Falls was completed in 1808.As soon as it had been built the Pontcysyllte aqueduct became famous for its highly innovativetechnical and architectural boldness. When completed it was recognised as an outstandingsuccess, eliciting praise from engineers and inspiring Romantic artists. After the end of theNapoleonic wars several foreign engineers and scholars came to visit the aqueduct.The Pontcysyllte aqueduct made Thomas Telford famous. He was recognised in his lifetime asthe greatest builder of iron bridges and canals of his time. He became the first president of theInstitution of Civil Engineers in London in 1825. Telford and his Pontcysyllte aqueduct had animportant influence in the international development of canals at the beginning of the 19thcentury in Great Britain, Europe and North America. Telford participated in the construction ofother very well known canals, such as the Caledonian Canal in Scotland and the Göta Canal inSweden.The economic influence of the canal for the region was considerable during the first half of the19th century, enabling the rapid development of coal extraction, metal working, limestonequarries, and the production of lime. The slate quarries of the Welsh mountains and agriculture
also benefited from the canal. By 1815 the substantial investments it had required had beenrepaid and the canal became a highly profitable business. Its direct link with a vast network ofcanals to the Mersey, through the Midlands, and as far as London, greatly encouraged the useof the canal.The situation here was different from that in other regions because the railway was not a directcompetitor to the canal but was instead basically complementary, through small private linesthat led up to the canal. However, the activity of heavy cargo transport went into a steepdecline at the end of the 19th century as the growth of local heavy industry contracted.Economic traffic dropped to a negligible level even before World War I.As the landscape environment remained rural and the valleys were pleasant - despite thepresence of industry, which never profoundly changed them - canal tourism began as early as1884. Throughout the first third of the 20th century canal tourism was both regular andorganised, in the form of small cruises and stays in countryside locations. However, the crisis ofthe 1930s, followed by the war, dealt the canal a fatal blow.In 1944 the Ellesmere Canal was decommissioned by an Act of Parliament, but its westernbranch was conserved, under the name of the Llangollen Canal, because of its role in theregional water supply. It was, however, in poor condition and no longer navigable, and theaqueduct therefore no longer carried any boats.Efforts to encourage pleasure cruising and the preservation of the industrial heritage, led byenthusiastic historians and writers, generated a renewal of interest in the early 1950s. This ledto a real lift-off for tourism in the 1960s in Great Britain, which contributed to the restoration ofthe canal and its maintenance. Since 1954 it has been managed and maintained in a navigablecondition by British Waterways. This canal is one of the most popular and frequented in theUnited Kingdom.During the 19th century the canal and its engineering structures were regularly maintained. Nostructural changes were made; wharves and buildings were, however, built on its banks to meettransport needs.The waterproofing of the Chirk Aqueduct was restored in 1866-68 with the addition of cast-ironplate sections at the ends. Some changes of individual metal parts have been carried out on thePontcysyllte Aqueduct; its towpath was relaid with cast-iron plates in 1879.Because of the relatively early decline of its industrial activity at the end of the 19th century, ithas not undergone any major transformation. It thus well reflects the Industrial Revolutionperiod and its waterway transport.Fill embankment collapses occurred in 1945, 1960, 1982 and 1985, requiring substantial repairwork at certain points on the canal. This was an important point to ensure the maintaining ofthe integrity of the waterway.The Pontcysyllte Aqueduct was completely renovated in 2003-2004 to mark its bicentenary,with every effort being made to respect its technical heritage. The work consisted of removing
corrosion on the cast iron, changing defective metal parts by others of the same form and ofsimilar materials, repairing the pier masonry, and completely restoring the towpath and itsrailings, which were in a poor state of repair.The Pontcysyllte Canal and Aqueduct have inspired canal preservation policy in Great Britainand have made a strong contribution to raising awareness of the heritage left behind by theindustrial period.TodayEveryone should experience a trip over Thomas Telford and William Jessops awe-inspiringPontcysyllte Aqueduct, by boat or on foot. It is a Scheduled Ancient Monument; a Grade I Listedstructure – and in June 2009 became a World Heritage site, putting it on an equal footing withthe Great Barrier Reef and Statue of Liberty. The aqueduct, taking the Llangollen Canal over thebeautiful River Dee valley, is 1000 feet long and 125 feet high. Such distances had never beforebeen conquered, until Telfords audacious decision to build it by laying an iron water-carryingtrough on stone piers. To this day, the joints are effectively sealed using a mixture of flanneland lead dipped in liquid sugar. For those crossing in a narrowboat, the effect is that of beingsuspended in mid-air. The iron trough sits about a foot above the water level and isunprotected on one side - so on one side of the boat there is nothing but 128 feet of air to thevalley floor below.You can also walk across the aqueduct, and the towpath is mercifullyprotected by a set of railings.