probably being atmospheric effects. Galileo also maintained their paths were straight, rather than circular, as Brahe and Grassi believed. As well as attacking Grassi, the Discourse also continued an earlier dispute with another Jesuit, Christoph Scheiner about sunspots. Grassi replied in turn with his treatise published under the pseudonym of Lotario Sarsi Sigensano (an anagram of Horatius Grassius Salonensis, his name in Latin). In this Grassi both noted how close the ideas in Galileo's Discourse were to those advanced by Gerolamo Cardano and Bernardino Telesio (which the Church regarded as dangerous) and set out scientific arguments and experimental test results to show that comets were definitely not optical illusions. Grassi's work provoked another furious reaction from Galileo in the shape of his 1623 work Il Saggiatore, in which he was savagely dismissive of Grassi's efforts. It has been suggested that Grassi was the author of an anonymous complaint to the Inquisition soon after appeared, asserting that the book advanced an atomic theory of matter, and that this conflicted with the Catholic doctrine of the Eucharist, because atomism would make transubstantiation impossible. Although most scholars do not agree that Grassi was its author, it is noteworthy that his second response to , the (1626), contains many of the same arguments as the anonymous complaint. While Libra had focused on mainly astronomical issues, Ratio focused on doctrinal issues. ... unlike The Assayer, which had recourse to the lethal polemical weapons of satire and the new philosophy, the Ratio used those no-less-lethal weapons of doctrinal and dialectical retort based on religious and philosophical orthodoxy. No further arguments were published on either side by Grassi or Galileo on these matters after this. Other scientific interests During the course of his career, Grassi wrote several other scientific and technical works, including one on spheres, clocks and optics ( (1617)); another on optics ( (1617)) and one on sundials in the works of Vitruvius ( (1624)). In the later period of his life, when he was in Genoa, he produced a number of other works, subsequently lost, including one treatise on the physics of light and another on architecture, unfinished at the time of his death. In 1644 he was also conducting experiments on atmospheric pressure based on the work of Evangelista Torricelli using a tube filled with mercury. These experiments were significant in demonstrating the inadequacy of Aristotelian physics. He continued to serve as Professor