[1] On 10 May 1881 Vandevelde was seconded to the Military Cartographic Institute, and joined the service of the Comité d'Etudes du Haut-Congo for three years in support of the Congo expedition of Henry Morton Stanley.

He spent a year at the marine engineering establishments, taking a practical course in mechanics and shipbuilding.

With his travelling companions, Edmond Hanssens, Théodore Nilis and Nicolas Grang, he went up the river to Vivi.

[2] In March 1883 there were rumors of a revolt, and Nilis, Vandevelde and Louis-Gustave Amelot went to come to the aid of Émile Parfonry, who was head of the Isangila station.

He delayed returning to the coast for treatment since he was needed by Stanley on the upper Congo, but became so ill that he had to be carried in a hammock through difficult country to Vivi.