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Rh principle of the Gallenians, contraria contrariis curari, is not always true."

We have repeatedly had occasion to quote from Tycho's letters. Both before and after he had become settled at Hveen, to all appearance for life, he kept up a correspondence with friends at home and with scientific colleagues abroad. Of the former, only Vedel and Dancey were left, and with these he occasionally exchanged friendly letters, but between him and the acquaintances he had made on his foreign travels very lengthy epistles passed as often as an opportunity offered of sending these by a carrier, merchant, or by some casual traveller. Among Tycho's principal foreign correspondents were Paul Hainzel and Johannes Major at Augsburg, Scultetus at Leipzig, the Emperor's physician, Hagecius, at Prague, and Brucæus at Rostock. Being always anxious to increase his library, Tycho in many of his letters inquires about new books, or asks his friends to procure them for him, especially such as were about the new star or the recent comets. These comets had also been observed by Hagecius, and Tycho pointed out the erroneous result his correspondent had come to in giving the comet of 1577 a parallax of five degrees, which would place it far within the sphere of the moon, whereas the observations made at Hveen showed that the horizontal parallax was less