CHT316934 Circle demonstrating colour differences and contrasts, from a book, \'Expose d\'un Moyen de definir et de nommer les couleurs\', by Eugene Chevreul, published in Paris by Firmin Didot in 1861 (colour litho) by French School, (19th century); Private Collection; (add.info.: 1er Cercle Chromatique renfermant les couleurs franches; Michel Eugene Franche (1786-1889) was a celebrated French chemist who also worked and wrote on colours; his work influenced neo-impressionist painters including Seurat and Signac; colour wheel); 穢 Archives Charmet; French, out of copyright.