One cannot fail but be impressed by the magic of this site.
Construction of the 7 locks at Rogny began under Henri IV in 1605, but was not finished until 1642. Its function was to take water from the Briare canal in the Trézée valley into the larger Loing valley. This was a very large structure for its time and continued in use until 1887. The traffic on the Briare canal is now carried by six more widely spaced locks, leading to a considerable time-saving.
The solution was devised by a civil engineer named Cosnier:
- Crossing the Rondeau plateau, which marked the catchment divide, between the Loire and the Seine, seemed impossible until Cosnier proposed a solution. Instead of following the Trézée, the canal headed for the Rondeau plateau where Cosnier devised a lock staircase supplied with water from nearby lakes. The Royal Council gave its approval to the new design on 30 December 1604.
- The locks (initially six in number with a seventh added later) covered a total length of 35 metres and were 5.15 metres wide. The locks were built adjacent to each other, which led to considerable cost savings (much to Sully’s taste) as the number of gates was halved. In addition, the structure gained in strength as the locks supported each other, as is shown by its current state of conservation.
Of course, two boats could not pass each other, but in the 17th century they very rarely had to as 90% of the boats were heading for Paris where they were broken up, mostly for firewood. This route was so well chosen that it was retained even when the canal was rehabilitated in 1882 after its return to State ownership.
Find out more :
- The view from Rogny-les-7-écluses (Format pdf - 71.5 kb - 29/02/2008)