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 concluded that they could have no parallax determinations.

In the same year, 1619, a Jesuit, Father Grassi, delivered a lecture on the three comets in the Roman College, in which he gave out that such phenomena were not mere appearances, but real heavenly bodies; copies of this lecture were widely circulated, and Galileo was strongly urged by his adherents to publish his opinion. He was prudent enough to evade for the time a fresh controversy, which, in the existing critical state of affairs, might bring him into danger, and apparently took no part in the scientific feud which was brewing. But he induced his learned friend and pupil, Mario Guiducci, consul of the Academy at Florence, to publish a treatise on comets. Numerous alterations and additions, however, which are found in the original MS. in the Palatina Library at Florence, attest that he had a direct share in the editorship. The opinions hitherto held by philosophers and astronomers on this subject were discussed, and the author's own—that is Galileo's—expounded. Grassi's views were sharply criticised, and he was reproachfully asked why he had passed over Galileo's recent astronomical discoveries in silence.

Grassi, who recognised the real originator of the work, in the reply which he issued a few months later entirely ignored the pupil, that he might the more vigorously attack the master. Under the pseudonym of Lothario Sarsi Sigensano, he published a pamphlet against Galileo, entitled, "The Astronomical and Philosophical Scales." It is written with