[FORTIFICATION]. A 17th century manuscript course on mathematics and fortification. In-4 of [58] ff, fawn calf, double gilt fillet, smooth spine decorated in the same way, smooth edges (Binding of the period). Superb manuscript illustrated with four title-frontispices, ten title cartouches and numerous figures artistically drawn in pen. The work is divided into four parts, the first three of which deal with De l'arithmétique (5 ff., without title); then De la géométrie pratique (12 ff., including title), with beautiful shaded geometrical figures; and finally De l'usage du compas de proportion (9 ff., including title), with 6 beautiful surveying figures in a landscape of ruins and 2 representations of the compass. The fourth part, the most developed, deals with Fortification proper (32 ff., including the title). Its two sections, Des places régulières and Des places irrégulières, are each decorated with a beautiful handwritten title-frontispiece and contain numerous full- and half-page diagrams of fortified places. The course of fortification approaches successively the Maxims of this art, the regular figures, of the square to the enneagon (which are summarized in a table with full page decorated with a beautiful cartouche with scrolls), Problems relating to it, the Works with horn and the Construction of the irregular places. Finally, it ends with a Discourse on fortification and General rules of fortification taken from the Traité ou manuel de la fortification by Gaston de Renty, published in Paris in 1639. Missing the initial title and possibly other introductory leaves, 2 ff. stained with ink, binding rubbed, missing headpieces and corners, spines split.