The idea of a 'canal in the sky' was ridiculed initially both by engineering sceptics and the canal builders themselves. Despite this, dozens of canal aqueducts have survived to become among the most inspiring of our waterway landmarks.
Although the use of floating water channels can be traced back to the days of the Roman Empire, aqueducts were not used for the passage of boats until the 15th century.
Early canal builders did not enjoy building aqueducts because the weight of the water meant they needed a very substantial masonry structure to support it. These problems eased slightly when they started using cast iron troughs in the late 18th century. Iron combines lightness with strength and rigidity; it was possible to support a cast iron trough on relatively slim masonry pillars.
The two great aqueducts of today, Edstone in England and Pontcysyllte in Wales, were both constructed using cast iron water troughs. Chirk was a masonry structure lined with cast iron plates. the primeval iron aqueduct still survives at Longdon on Tern in Shropshire.
As part of the construction of the renowned Pontcysyllte Aqueduct, ox blood was added to the lime mortar used to bind the masonry together. This followed the ancient superstition that the blood of a strong animal would strengthen a building or structure.
History was also made in 1893 with the construction of the pioneering Barton Swing Aqueduct. Sir Edward Leader Williams came up with this novel solution to the problem of large boats passing beneath an aqueduct. The 235’ long ‘swinging’ aqueduct pivots open to make room for vessels travelling on the Manchester Ship Canal.
Last date edited: 7 July 2015