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Rh The book was dedicated to the Emperor Rudolph II., whom Tycho was now specially anxious to interest in his labours. The dedication, which is dated the 31st December 1597, refers shortly to the instruments of the ancients and the limited accuracy attainable with them, and gives a summary of the contents of the book. Then follow (after a poem by Holger Rosenkrands) figures and descriptions of the seventeen principal instruments used at Uraniborg and Stjerneborg; of the sextant used in 1572–73 (two figures), of the great quadrant at Augsburg, and of a mounting once used for the largest azimuthal quadrant, and superseded by the one figured as No. 7. We shall not here dwell on these descriptions of Tycho's instruments, as they will be considered in some detail in the last chapter, and some of them have already been alluded to in previous chapters. It was natural that Tycho should at that time, with an uncertain future before him, point with some satisfaction to the convenient construction even of the larger instruments, which enabled him to take them asunder for the sake of transportation to different parts of the world. For an astronomer must be cosmopolitan ("Oportebit enim Astronomum esse "), as among statesmen there are rarely found any who admire his studies, but frequently those who despise them. But the student of this divine art should not care about the opinions of ignorant people, but only think of his studies, and if interfered with by politicians or others, let him move himself and his belongings to some