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Pontcysyllte Aqueduct

Pontcysyllte Aqueduct - Overview

The Pontcysyllte Aqueduct was constructed between 1796 and 1805 to carry the Ellesmere Canal over the River Dee, linking the Froncysyllte and Trefor villages situated on either side of the valley. It was designed and built by civil engineer Thomas Telford, acting as General Agent, and the more experienced consulting engineer William Jessop who undertook the site surveys and advised on best courses of action. The construction of Pontcysyllte Aqueduct cost £47,000. Standing 39 metres tall and 307 metres across, it is now the longest navigable aqueduct in Great Britain and the tallest in the world.

The aqueduct consists of eighteen stone piers that carry a cast iron trough which forms the canal. The piers are hollow and taper towards the top in an effort to reduce their weight and so allow for such a tall construction. For mortar, it is said, the engineers relied on a mixture of lime, water and ox blood. The cast iron trough is not fixed to the stone work, but merely sits on top of the series of sprung iron ribs which rise from each pier and is anchored by the weight of the water alone. The original towpath was replaced in 1831 by a cantilevered design that allowed the water displaced by passing boats to flow underneath it, reducing drag.

The aqueduct was constructed at the time of the emergence of modern tourism in Wales. Among the early continental visitors was the Archduke John of Austria who, with the end of the Napoleonic Wars, took the opportunity of travelling to Wales in 1816. Praising the beauty of the Dee valley in general, he then particularly recommended viewing the canal from below because it allowed a better appreciation of the intricate construction design. Other visitors were less interested in the engineering aspects of the aqueduct, but appreciated it more for its architectural beauty and harmony with the surrounding landscape. On 22 June 1830, the French landscape artist Alphonse Dousseau produced a faithful watercolour drawing of Pontcysyllte Aqueduct, complete with iron railing and set against the backdrop of the picturesque Dee valley at sunset and with a view of the ruins of Castell Dinas Brân in the far distance.

In 2009, Pontcysyllte Aqueduct was inscribed as World Heritage Site by UNESCO, recognising its innovative engineering design and great significance for the historical development of British waterways.

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