This is a movable quadrant with a radius of two and a half Bolognese feet (c. 100 cm), with stand and frame in iron and brass limb, fitted with two telescopes, one fixed the other movable. We know from the 1727 inventory and the 1780 revision of the guide to the Istituto delle Scienze in Bologna that it had been donated to the Accademia delle Scienze in 1725 by cardinal Antonio Davia who for several years had a small specola in his home: "Ex munere Emi. Card. De Via/ Quadrans Astronomicus semid. 2 ½, compagine ferrea, centro ac limbo auricalceo, telescopiis duobus, suppedaneo, et axibus tribus ferreis.".
It had been made in 1710 by the Bolognese watch-maker Sante Menini, as witness the inscription in the central brass escutcheon - Sante Menini orologiere/ in Bologna 1710 - under the motto Suum volvens/ audax industria/ mundum.
We know from the correspondence of the Genoese marquis Paride Maria Salvago to Manfredi, dated 19 March, 6 April and 14 March 1712 (Arch. Dept. Astron. Bo. bag XXXVII) that the instrument was very successful and that other quadrants were ordered from Menini. At a certain point, however, he turned down the many requests he received on account of the harm caused him engraving scales of this size which he did using nitric acid. The decision was perhaps somewhat belated, since shortly after the craftsman was to die.
One of the telescopes is missing together with the object lenses of the second which apparently was the movable one. The connection to the limb has been restored (G. Morigi, Bologna 1979). Of all the quadrants at the Specola this is the only one that still has its joint which allowed it to be used as an astronomical sextant.
E. Baiada, A. Braccesi (1983) pp. 89 and 100-101, fig. 12a-12b
Notizie dell’Origine e Progressi dell’Instituto delle Scienze di Bologna (1780) p. 185.