In his final years his son Eugène-Louis became the head of the Commission of Historic Monuments. He took on just one new project, the restoration of the cloister of the Augustines at Toulouse. He completed his series of dictionaries of architectural periods, designed for a general audience. He also devoted more time to studying the geography of the Alps around Mont-Blanc. He spent his summers hiking in the mountains and writing articles about his travels. He launched a public campaign for the re-forestation of the Alps, and published a detailed map of the area in 1876. He spent more and more time at La Vedette, the villa he constructed in Lausanne, a house on the model of a Savoyard chalet, but with a minimum of decoration, illustrating his new doctrine of form following function. He made one last visit to inspect Carcassonne, whose work was now under his son's direction. After an exhausting summer of hiking in the Alps in 1879, he became ill and died in Lausanne on 17 September 1879. He was buried in the cemetery of La Sallaz in Lausanne. In 1946 his grave and monument were transferred to the Cemetery of Bois-le-Vaux (Section XVIII) in Lausanne.