4to. [21 x 14.5 cm], (I)-X pp. including title-page, (1) ff. imprimatur, (1) ff. engraved folding plate. Bound in later vellum. Woodcut devices on first 2 ff.. Ex libris on front-end pastedown, light foxing or staining to title-page and leaves. Generally good.
Extremely rare first edition of an instruction manual for a new nautical instrument that determines “l’angolo di deriva,” i.e. a ship’s drift angle (a result of yaw). At times Micheli’s tract also recounts the public success of his previous inventions: in 1774 he was commissioned by the Grand Duchy of Tuscany to update the official distances of local roads, evidently earning the praise of the Grand Duchess; later that year, he invented a nautical odometer and mounted it on the frigate Rondinella, noting that the ship’s captain and his officers bore approving witness to its accuracy and ease of use.
Micheli’s newest instrument is depicted, both complete and dismantled, in a single folding plate. It consists of a quadrant affixed to a brass plate, which itself is attached to a ship’s stern, and two freely swinging needles: one to mark degrees on the quadrant, and the other attached to a plumbline with a flat, triangular weight. The line is dropped into the sea, and when the ship’s prow departs from its intended heading, the shift in current moves the weight to one side, yanking down the needles and displaying the drift angle on the quadrant. The work is addressed to “Professori di Nautica.”
We locate just one copy (with misspelled title – ‘machina’ for macchina) on OCLC, held by the BSB in Munich. ICCU identifies a further 3 copies in Italian libraries.