IRSON (Claude).L'Arithmétique universelle démontrée. Paris : L'Auteur, Pierre Baudoüyn, 1674. - In-4; 245 x 175 : (8 ff.), 319 pp. Red morocco, boards decorated with Duseuil-style gilding, ornate ribbed spine, gilded edges (period binding).Very rare first edition, dedicated to François Bellinzani (1619-1684), a trafficker who became director of the Paris Chamber of Commerce. This is a manual of applied arithmetic, written by the mathematician and grammarian Claude Irson (16..-16..). It contains "in six main rules arranged in a natural order, applications suitable for Finance & Banking & Merchandise Trading; Military Art & Practical Geometry" (title). One of the first and most important treatises of its kind, it was reprinted several times, notably in 1678 and 1692, before an abridged version was proposed in 1695. An exceptionally fine copy in contemporary red morocco. Very skilful restoration to binding. Endpapers renewed. Perfect condition inside.