Iron Trunk Aqueduct

The Grand Junction Canal (later absorbed into the Grand Union Canal) required to cross the course of the River Great Ouse, the lowest point between the summits at Tring and Braunston. Initially flights of locks, four at the southeast and five at the northwest, were used to allow the canal to descend to cross the river on the level, and this arrangement came into action in 1800. However William Jessop, the canal company’s engineer, designed a three-arch brick viaduct so that the canal could cross at a higher level, reducing the water loss and delay in locking down to river level. His structure was opened on 26 August 1805, but a section of the canal embankment collapsed in January 1806; this…

As a temporary measure the lock system originally installed was brought back into use, and Benjamin Bevan, an engineer employed by the canal company, designed a replacement structure. By this time, cast iron trough aqueducts designed by Thomas Telford for the Pontcysyllte Aqueduct and elsewhere, had become proven, and Bevan adopted the system for his structure. However, the canal was then operating as a wide canal in contradistinction to some northern narrowboat canals, so that the troughs had to be substantially larger and stronger than elsewhere. The cast iron units were cast at the Ketley foundry at Coalbrookdale; the company had already been involved with Telford on the Longdon-on-Tern…