Darcy’s first challenge, at age 29, was to provide abundant, clean, free water for Dijon’s inhabitants, a project that had been discussed for five centuries and was considered “worthy of the Romans.” After examining and gauging surface and ground water sources in and near Dijon, Darcy chose as his source the Rosoir spring, located 12.7 km NW of Dijon. The project involved construction of an aqueduct to bring the water to Dijon and, for city distribution, two reservoirs (total capacity = 5490 m³), 6 km of masonry aqueducts, 12 km of cast iron pipes, and 16 km of additional piping to supply 142 street fountains. The aqueduct was begun in 1838 and completed in 1839. Municipal distribution was completed in 1844.

Darcy next tackled the railroad. The Paris-to-Lyon line was the most important spoke in France’s proposed rail system. An 1842 law specified that the line pass through Dijon, but a topographic divide between the Seine and Saone basins posed a major obstacle. At a time when tunnels inspired fear in many people, Darcy proposed a 4.1 km tunnel at Blaisy, 26 km W of Dijon, to cross the divide and connect Paris and Dijon. Geologist Elie de Beaumont examined the Jurassic limestone in the tunnel’s path and declared the rock sound. Darcy’s plan was adopted. Darcy supervised tunnel construction from January 1845 until July 1846, when a private concession took over. The TGV uses the Blaisy tunnel to this day.

Darcy’s third project is the porous media experiments conducted in 1854-55. These led to Darcy’s law, the quantitative basis of hydrogeology. Darcy did the experiments in a courtyard of Dijon’s general hospital, which was founded in 1204 and expanded and renovated over the centuries. In 1844 Darcy’s water supply system replaced the hospital’s shallow courtyard wells, thereby providing the abundant water supply that Darcy needed for the sand experiments. The exact location of the experiments is unknown, but as we tour the courtyards by photo, we know we are in Darcy’s laboratory. The hospital has moved to a new site; the historic buildings are being renovated to host the Cité internationale de la gastronomie et du vin, scheduled to open in Spring 2022.