Sunday, 31 May 2009

Longdon on Tern Aqueduct

Longdon on Tern Aqueduct
Shrewsbury Canal
31st May 2009

This aqueduct is as fascinating as it is remote.

The aqueduct was originally assigned to Josia Clewes who started work on a conventional stone structure but whose sudden death in 1795 caused responsibility to pass to Thomas Telford.

The aqueduct looks like a bit of a hybrid, and so it it. The stone abutments at the end are the remaining sections of the original stone aqueduct, the central section of which was washed away in floods before completion.

My thanks to NB Starcross for this photo.

Telford was looking for an alternative approach to aqueduct construction, which would allow him to go longer and higher. Having seen an early application of cast iron used in an aqueduct on the Derby Canal, he devised the Longden on Tern trough we see today - 62 feet long (of an overall 187 ft), 3 feet deep and 9 feet wide. This trough then sits on three slender piers bedded into masonry.

Telford learned from this structure, moving on the the magnificent Pontcysyllte, using the best of Longden on Tern but improving the ease of use by widening the trough and cantilevering the towpath over it. This allows water to move more easily around a passing boat, easing its passage.
The trade to Coalbrookdale dried up and the canal was abandoned in 1944,then de watered in the 1950's. The structure is now Grade one listed and a scheduled ancient monument to boot.

Fascinating eh?

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