GRASSI, ORAZIO. - Jesuit, born in Savona ca. 1583, died in Rome on 23 July 1654. He entered the Society at the age of eighteen; he taught mathematics in Genoa and later in Rome.
There he composed the treatise *De tribus comitis* (Rome 1619) to clarify the nature of the three comets that appeared in 1618, to which Mario Guiducci replied with the *Discorso delle comete* (Florence 1619), GALILEA (v.). Grassi responded under the pseudonym Lotario Sarsi with the treatise *Libra astronomica ac philosophica* (Perugia 1619), and later again with his *Ratio ponderum librae et libellae* (Paris 1626). According to Guiducci, Grassi did not appear entirely opposed to the motion of the earth. In 1626 he served as the architect of the church of S. Ignazio in Rome and prepared its model for Cardinal Ludovisi in 1628–29; the church was completed in 1685 according to his design.