IRSON (Claude) L'Arithmétique universelle démontrée. Paris: L'Auteur, Pierre Baudoüyn, 1674. - In-4; 245 x 175 : (8 ff.), 319 pp. 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, the applications suitable for Finance & Banking & Merchandise Trading; Military Art & Practical Geometry" (title). It was one of the first and most important treatises of its kind, and was reprinted several times, notably in 1678 and 1692, before an abridged version was published in 1695. A copy in contemporary red morocco, in the most precious condition. Very skilful restoration to the binding. Endpapers renewed. Perfect condition inside.