Iron trough aqueduct, 1794.
© Science Museum / Science & Society Picture Library
Design for an aqueduct by Thomas Telford. Pontcysyllte Aqueduct, also known as Llangollen Aqueduct was designed by the civil engineer Thomas Telford (1757-1834) to carry the Llangollen Branch of the Shropshire Union Canal over the valley of the River Dee. Built in 1795-1805, Telford's finished design involved a cast iron trough supported on stone piers to carry the water of the canal (and boats) 125 feet above the river. The aqueduct was 1000 feet long.