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 caustic bitterness, and is a model of Jesuitical malice and cunning. The comet question was for the time a secondary matter with Grassi, and he begins with a personal attack on Galileo, by disputing the priority of several of his most important discoveries and inventions, and reproaching him, with pious indignation, with obstinate adherence to a doctrine condemned by theologians. Up to this point he is only angry and spiteful, but as he goes on he becomes cunning. He sets up for a warm defender of the Peripatetic physics, and attacks the Copernican system, and its advocate Galileo, to compel him either to ignominious silence or dangerous demonstrations. Under pretext of meeting Guiducci's reproach that he (Grassi) had taken Tycho as his authority, he asks whether it would have been better to follow the system of Ptolemy, which had been convicted of error, or that of Copernicus, which every God-fearing man must abhor, and his hypothesis, which had just been condemned? In discussing the causes of the movements of comets, it seemed to him that the arguments were insinuated on which the forbidden doctrines were based. "Away!" he exclaims in righteous indignation, "with all such words so offensive to truth and to every pious ear! They were prudent enough certainly scarcely to speak of them with bated breath, and not to blazon it abroad that Galileo's opinion was founded upon this pernicious principle."

Thus attacked, Galileo prepared to defend himself. The greatest caution was necessary, for Grassi was backed by the powerful party of the Jesuits, who made a great boast of this work. The letters of this period from Prince Cesi and Galileo's ecclesiastical friends at Rome show that they were very anxious that he should not make the influential order of Jesuits his enemies by a direct collision with them. But as they saw the absolute necessity of a reply, they gave him all sorts of good advice, how to parry the attack without