Description

Built between 1795 and 1808, the Pontcysyllte Aqueduct and Canal comprise an exemplary group of civil engineering features from the heroic phase of transport improvement that accompanied the Industrial Revolution. The Principal Engineer for the canal was William Jessop (1745-1814), one of the most important canal and dock engineers of the day. The General Agent was Thomas Telford (1757-1834), then a little known county surveyor, but to become the most prolific civil engineer of the early nineteenth century. Owing to its particular daring and elegance, the Pontcysyllte Aqueduct is regarded as a spectacular masterpiece of waterways engineering and an influential pioneer of iron construction. The sections of canal that extend c.10 km to the west (to Llantysilio) and c. 6 km to the south (to Chirk) from the aqueduct exemplify the new approaches to engineering developed in Britain during the Industrial Revolution and taken up in subsequent waterway, railway and road construction throughout the world. All of the features that were to become characteristic of heavily-engineered transport routes can be seen along the canal: features such as tunnels, cuttings, aqueducts and embankments, many of them technically innovative or of monumental scale, together with associated bridges, culverts and weirs.

Pontcysyllte Aqueduct and Canal are part of the Ellesmere Canal scheme that was promoted by Act of Parliament in 1793. The primary purpose of the scheme was to permit industrial development in the Denbighshire coalfield by linking it to external markets. The canal carried boats hauled by horse from a parallel towing-path. The main line of the canal ends at Trevor Basin, on the north side of Pontcysyllte Aqueduct. The Llangollen Branch of the canal extends to the west from Trevor Basin, along the north bank of the steep-sided Vale of Llangollen. Although proposed as early as 1791 it was begun under an Act of Parliament of 1804 and completed in 1808. Its purposes were to serve the town of Llangollen and adjacent industries and to bring a large and reliable supply of water into the main canal system from a new weir on the River Dee at Llantysilio. This section of canal was narrower than the main line, but achieved a similarly direct and level route by way of considerable engineering works. The canal is at its narrowest in its last section, from Llangollen to Llantysilio, where its primary function is as a water feeder. The extraction point is the Horseshoe Falls, an elegant, curved cast-iron and masonry weir on the River Dee that was built to supply the canal.

The monument is of national importance as the masterpiece of two exceptional figures from the heroic phase of civil engineering in the late eighteenth and early nineteenth centuries, reflecting the crucial developments within inland navigation, civil engineering and the use of iron. It is an outstanding example of the pivotal importance of transport improvement to the Industrial Revolution. As the largest civil engineering projects of their day, canal construction projects were responsible for numerous organisational and technical innovations. Pontcysyllte Aqueduct and Canal is an exemplary manifestation of the innovations which produced the British canals system and were carried forward into the development of later railways, roads and industrial projects. In organisation, innovations included principles of contract management, delegation of duties within engineering teams and the professional independence of engineers. In technology, innovations included hollow masonry and new waterproofing methods to reduce weight, composite use of cast iron and stone, earthwork calculations, construction railways, barrow inclines and cut-and-cover tunnels.

The outstanding feature of the Scheduled Ancient Monument is the Pontcysyllte Aqueduct, originally scheduled in 1958. However, the original designation did not reflect the sophistication of the engineering of the canal or the importance of the earlier Chirk Aqueduct (where Thomas Telford and William Jessop experimented with the use of cast iron) and the Schedule entry has been revised to include the entire length of the Llangollen Branch (including the weir at the Horseshoe Falls and the Pentrefellin Aqueduct), Trevor Basin and the heavily engineered canal section south of Pontcysyllte (including the Froncysyllte Embankment; the Chirk Tunnel and Whitehouse Tunnel; the Canal Wood Cutting and Irish Bridge Cutting; and the Chirk Basin and Aqueduct).

The scheduled area comprises the remains described and an area around them within which related evidence may be expected to survive. The scheduled area includes the canal, its towpath and immediate banks, cuttings and embankments. Where the canal comprises an architectural structure (such as an aqueduct or tunnel), that architectural structure is included in its entirety. Where the canal comprises an earthwork structure (such as an embankment or cutting), that earthwork structure is included in its entirety. Excluded from the schedule are the Llangollen Marina, the Chirk Marina and the many over bridges and associated buildings that line the canal and its wharves and basins (most of which are more appropriately protected under the Planning [Listed Buildings and Conservation Areas] Act 1990).

Source: Cadw