Duncombe's proposal for a full-height masonry aqueduct, designed to carry the Llangollen Canal over the River Dee in Wales. The plan which was eventually chosed for the Pontcysyllte Aqueduct was designed by the civil engineer Thomas Telford (1757-1834) and was also known as Llangollen Aqueduct. 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.
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