Timeline

Heritage classified

Key figures

Origin and history

The graduation of the Saline d'Arc-et-Senans was built between 1775 and 1779, at the same time as the royal saline, under the direction of architect Claude-Nicolas Ledoux. It was located at the end of the Salins-les-Bains to Arc-et-Senans Saumoduct for a distance of 21 km. Its role was to increase the salt concentration of the brine prior to its passage into the saline evaporation stoves. The process was based on a 496-metre-long and 7-metre-high wooden structure, where salt water, distributed by a drilled pipe, drained onto thorns to promote natural evaporation under the influence of wind.

The graduation building operated with a complex hydraulic system: a bypass channel operated a blade wheel, which supplied a pump to raise the brine. After several evaporation cycles, the brine, carried to a salinity of about 24 degrees, was collected in a 900 m3 basin before being sent to the saline. This device, innovative for the time, allowed to optimize the production of salt by concentrating the brine before its final treatment.

When the salt was closed in 1895, the graduation building was almost completely destroyed in 1920, with the exception of the hydraulics and the carpenter's housing, which was responsible for its maintenance. These remains, including the canal, the remains of the pump wheels and the carpenter's house (facades and roof), were listed as historic monuments on October 8, 1991. Today, they bear witness to the technical ingenuity deployed in the 18th century salt industry.

The graduation was located on the current rue des Graduations in Arc-et-Senans, along a straight road leading from the Loue to the royal saline. This site, designed by Ledoux, was part of an ambitious architectural and industrial project aimed at modernising salt production in Franche-Comté. The preserved remains provide a rare glimpse of brine concentration techniques, now extinct.

The graduation process, although specific to Arc-et-Senans, was based on European techniques used in other salt ponds. The wooden structure, now extinct, was a technical feat for the time, combining hydraulic mechanics and natural ventilation. Its operation was based on a specialized workforce, such as the carpenter who was housed on site, whose role was crucial to maintaining the facility.

External links