Telford’s triumph

Pontcysyllte Aqueduct, Ellesmere Canal

Pontcysyllte Aqueduct, Ellesmere Canal

Pontcysyllte is one of the major triumphs of British canal engineering, and the most spectacular travellers’ experience on British waterways, whether you walk or sail across it.  The 1,007-foot long aqueduct carries the waters of the Ellesmere Canal 126 feet above the River Dee.

Vertigo can be a problem.  Whenever I’ve taken groups to Pontcysyllte there’s no guarantee they’ll all walk the length of the towpath, despite the protection of railing five feet high;  indeed, I know of people who only managed to sail across by lying on the floor of their boat with their eyes closed.

Industrial archaeologists argue over how to apportion credit for this magnificent structure.  The engineer of the Ellesmere Canal was William Jessop (1745-1814), well-established, busy and – it has to be admitted – not always successful in building masonry aqueducts.  At the Dee crossing, one of Jessop’s team had suggested dropping the canal down each side of the valley by flights of locks to a low-level three-arch aqueduct:  this idea amounted to throwing two lockfuls of water away for every boat that crossed.  Jessop pointed out that a smaller number of locks feeding into a taller aqueduct would save a third of construction costs, but still use up huge amounts of water.

When Thomas Telford (1757-1834) was appointed to take direct charge of constructing the canal, with Jessop as consultant, he pointed out that building an iron-trough aqueduct across the valley at the height of the canal would actually cost no more to construct and would speed up traffic by eliminating lockage without any loss of water whatsoever.

Using cast iron for this purpose was a new and virtually untried technique.  Telford took the opportunity to field-test the principle when he took over as engineer of the Shrewsbury Canal and completed the Longdon-on-Tern Aqueduct (1796), and then rehearsed it further down the Ellesmere Canal at Chirk Aqueduct (1801) before ordering the ironwork for Pontcysyllte, which was completed and opened in 1805.

Visiting Pontcysyllte is an unmissable experience, whether by boat or on foot.  From there it’s possible to walk down to Chirk Aqueduct and back within half a day, or to walk into Llangollen in an hour or so.  A more relaxing experience, starting from Llangollen Wharf, is to catch a horse-drawn trip-boat to Pontcysyllte, or a diesel boat across the aqueduct (one way, with a return journey by courtesy coach):  Llangollen Wharf – Aqueduct Trips (

The best experience of all, though, once every five years when the ironwork is inspected, is when the waterways engineers pull the plug in the aqueduct bed, sending the canal water cascading down to the Dee.  You have to get up early for that.

2 thoughts on “Telford’s triumph

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