AUDIFFREDI, GIOVANNI BATTISTA. — Dominican astronomer and bibliographer, born at Saorgio (Nice) on 2 Feb. 1714, died in Rome on 4 July 1794. After several years of teaching, in 1759 he was elected prefect of the Casanatense Library in Rome, a position he held until his death. There, with very limited resources, he established an astronomical cabinet, observing the transits of Mercury (1753 and 1756) and Venus (1761), studying eclipses and the motions of the moon (1754 and 1755), the solar parallax (1765), and the theory of comets (1769).
Monuments to his bibliographical activity include the *Catalogus Bibliothecae Casanatensis*, Rome 1761–88 (up to the entry *Leodegarius*, 4 vols. in-fol. and a fascicle), compiled with new criteria that reveal his profound learning; the *Catalogus historico-criticus Romanarum editionum saec. XV*, ibid. 1783; and the *Specimen historico-criticum editionum italicarum saec. XV*, ibid. 1794; works of great value and utility.