 Vieillard published in several newspapers, mainly in the former "Moniteur universel", many articles that reflected the breadth and variety of his knowledge.He also became one of the principal editors of the "Encyclopédie des gens du monde", where he was specially commissioned to write biographies about famous men of the French Revolution.Well versed in the history of that time, which he lived, the moderation of his opinions and the uprightness of his character let him naturally assess accurately the events and actors.