[2] The Trans-Saharan expedition was appointed in 1879 by Charles de Freycinet, Minister of Public Works, to investigate construction of a railway across the Sahara.
Three possible routes starting from Oran in the west, Algiers in the center and Constantine in the east were to be examined by three expeditions.
[5] The eastern route was considered the most dangerous, going via the Hoggar Tuareg town of Rhat.
In 1897 the post of Inspector General for Algeria, based in Algiers, was created especially for him in recognition of his great merit.
He retired in September 1900, and gave up the direction of the geological map, which he had been working on for 20 years.