The Pontcysyllte Aqueduct and Canal are located in northeast Wales and were constructed in the late 18th and early 19th centuries. The Pontcysyllte Aqueduct, designed by renowned civil engineer Thomas Telford, is over 1000 feet long and supported 126 feet above the River Dee by 19 hollow masonry piers. It was a pioneering work that demonstrated the potential of cast iron in construction. Today, the aqueduct and canal are protected as a UNESCO World Heritage Site and remain an important example of Britain's Industrial Revolution and waterway transportation infrastructure.

1. Pontcysyllte Aqueduct and Canal
Situated in north-eastern Wales, the 18 kilometre long Pontcysyllte Aqueduct and Canal are
remarkable examples of the construction of a human-engineered waterway in a difficult
geographical environment, at the end of the 18th century and the start of the 19th century. It
required extensive and boldly conceived civil engineering works. The Pontcysyllte Aqueduct is a
pioneering masterpiece of engineering and monumental architecture by the famous civil
engineer Thomas Telford. It was constructed using metal arches supported by tall, slender
masonry piers. The Pontcysyllte Aqueduct and Canal are early and outstanding examples of the
innovations brought about by the Industrial Revolution in Britain, where they made decisive
development in transport capacities possible. They bear witness to very substantial
international 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 seven
wonders of the British Inland Waterways System. It is of course still used for its original
purpose, being crossed by more than a thousand canal boats a year. Moreover, people walk
across it. The footpath, protected on one side by a metal railing, is just about wide enough for a
wheelchair, but there’s no barrier between the path and the narrow canal trough running
alongside it.
The aqueduct helps the Llangollen Canal continue across the valley of the River Dee, in
Wrexham in north east Wales. Its cast-iron trough is 1,007 feet long, 11 feet wide and 5.25 feet
deep, and accommodates canal boats. It is supported 126 feet above the riverbed by iron
arched ribs carried on 19 hollow masonry piers. Each span is 53 feet across.
During the aqueduct's 10 years of planning and construction, Telford fought past a public
skeptical that his design of cast-iron plates fixed in masonry would work; his experience
working 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 aqueduct
was known as Pont y Cysyllte. In 2009, it achieved global landmark status when the United
Nations designated Pontcysyllte Aqueduct a UNESCO World Heritage Site.

2. Historical Description
In 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 company
under the technical supervision of the engineer William Jessop (1745-1814). The construction
of three branches was started from the central point of Ellesmere. The need for water and the
rich reserves of coal and limestone in the Dee and Ceiriog valleys, in the foothills of the Welsh
mountains, led to the extension of the project in this direction by a fourth section. The works
began in 1795.
However, linking the northern side of the Dee to the Ellesmere canals, crossing the Rivers
Ceiriog and Dee, which have very pronounced valleys, presented two major obstacles. From
1793 onwards, Jessop worked in collaboration with Thomas Telford (1757-1834) for this branch
of the canal. Telford was an outstanding engineer and architect who had a remarkable ability
for finding new technical solutions to building and civil-engineering problems. He was already
well known when he was engaged and had just undertaken the construction of several cast-iron
bridges, such as the Longdon aqueduct to cross the Severn. He also proposed a cast-iron bridge
to cross the Thames. In the same region he was also employed to build the road from London
to Dublin.
The aqueduct over the Ceiriog at Chirk was the first structure to be planned, in 1795, by Jessop
and 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. The
valley was wider and deeper, and a conventional aqueduct would therefore have been be very
costly; furthermore, cast-iron bridges were beginning to prove their qualities. The cast-iron
bridge solution proposed by Telford was chosen and construction work began under his
supervision. The canal up to Trevor was opened on 26 November 1805. The part which extends
the canal to Horseshoe Falls was completed in 1808.
As soon as it had been built the Pontcysyllte aqueduct became famous for its highly innovative
technical and architectural boldness. When completed it was recognised as an outstanding
success, eliciting praise from engineers and inspiring Romantic artists. After the end of the
Napoleonic wars several foreign engineers and scholars came to visit the aqueduct.
The Pontcysyllte aqueduct made Thomas Telford famous. He was recognised in his lifetime as
the greatest builder of iron bridges and canals of his time. He became the first president of the
Institution of Civil Engineers in London in 1825. Telford and his Pontcysyllte aqueduct had an
important influence in the international development of canals at the beginning of the 19th
century in Great Britain, Europe and North America. Telford participated in the construction of
other very well known canals, such as the Caledonian Canal in Scotland and the Göta Canal in
Sweden.
The economic influence of the canal for the region was considerable during the first half of the
19th century, enabling the rapid development of coal extraction, metal working, limestone
quarries, and the production of lime. The slate quarries of the Welsh mountains and agriculture

3. also benefited from the canal. By 1815 the substantial investments it had required had been
repaid and the canal became a highly profitable business. Its direct link with a vast network of
canals to the Mersey, through the Midlands, and as far as London, greatly encouraged the use
of the canal.
The situation here was different from that in other regions because the railway was not a direct
competitor to the canal but was instead basically complementary, through small private lines
that led up to the canal. However, the activity of heavy cargo transport went into a steep
decline 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 the
presence of industry, which never profoundly changed them - canal tourism began as early as
1884. Throughout the first third of the 20th century canal tourism was both regular and
organised, in the form of small cruises and stays in countryside locations. However, the crisis of
the 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 western
branch was conserved, under the name of the Llangollen Canal, because of its role in the
regional water supply. It was, however, in poor condition and no longer navigable, and the
aqueduct therefore no longer carried any boats.
Efforts to encourage pleasure cruising and the preservation of the industrial heritage, led by
enthusiastic historians and writers, generated a renewal of interest in the early 1950s. This led
to a real lift-off for tourism in the 1960s in Great Britain, which contributed to the restoration of
the canal and its maintenance. Since 1954 it has been managed and maintained in a navigable
condition by British Waterways. This canal is one of the most popular and frequented in the
United Kingdom.
During the 19th century the canal and its engineering structures were regularly maintained. No
structural changes were made; wharves and buildings were, however, built on its banks to meet
transport needs.
The waterproofing of the Chirk Aqueduct was restored in 1866-68 with the addition of cast-iron
plate sections at the ends. Some changes of individual metal parts have been carried out on the
Pontcysyllte 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, it
has not undergone any major transformation. It thus well reflects the Industrial Revolution
period and its waterway transport.
Fill embankment collapses occurred in 1945, 1960, 1982 and 1985, requiring substantial repair
work at certain points on the canal. This was an important point to ensure the maintaining of
the 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

4. corrosion on the cast iron, changing defective metal parts by others of the same form and of
similar materials, repairing the pier masonry, and completely restoring the towpath and its
railings, which were in a poor state of repair.
The Pontcysyllte Canal and Aqueduct have inspired canal preservation policy in Great Britain
and have made a strong contribution to raising awareness of the heritage left behind by the
industrial period.
Today
Everyone should experience a trip over Thomas Telford and William Jessop's awe-inspiring
Pontcysyllte Aqueduct, by boat or on foot. It is a Scheduled Ancient Monument; a Grade I Listed
structure – and in June 2009 became a World Heritage site, putting it on an equal footing with
the Great Barrier Reef and Statue of Liberty. The aqueduct, taking the Llangollen Canal over the
beautiful River Dee valley, is 1000 feet long and 125 feet high. Such distances had never before
been conquered, until Telford's audacious decision to build it by laying an iron water-carrying
trough on stone piers. To this day, the joints are effectively sealed using a mixture of flannel
and lead dipped in liquid sugar. For those crossing in a narrowboat, the effect is that of being
suspended in mid-air. The iron trough sits about a foot above the water level and is
unprotected on one side - so on one side of the boat there is nothing but 128 feet of air to the
valley floor below.You can also walk across the aqueduct, and the towpath is mercifully
protected by a set of railings.