of Tycho Brake 131 



by trying to estimate and to allow for the errors of his 

 instruments. 



In 1565 Tycho returned to Copenhagen, probably on 

 account of the war with Sweden which had just broken out, 

 and stayed about a year, during the course of which he lost 

 his uncle. He then set out again (1566) on his travels, 

 and visited Wittenberg, Rostock, Basle, Ingolstadt, Augsburg, 

 and other centres of learning, thus making acquaintance 

 with several of the most notable astronomers of Germany. 

 At Augsburg he met the brothers Hainzel, rich citizens 

 with a taste for science, for one of whom he designed and 

 had constructed an enormous quadrant (quarter-circle) 

 with a radius of about 19 feet, the rim of which was 

 graduated to single minutes ;.and he began also here the 

 construction of his great celestial globe, five feet in diameter, 

 on which he marked one by one the positions of the stars 

 as he afterwards observed them. 



In 1570 Tycho returned to his father at Helsingborg, 

 and soon after the death of the latter (1571) went for 

 a long visit to Steen Bille, an uncle with scientific tastes. 

 During this visit he seems to have devoted most of his 

 time to chemistry (or perhaps rather to alchemy), and his 

 astronomical studies fell into abeyance for a time. 



100. His interest in astronomy was fortunately revived 

 by the sudden appearance, in November 1572, of a brilliant 

 new star in the constellation Cassiopeia. Of this Tycho 

 took a number of extremely careful observations ; he noted 

 the gradual changes in its brilliancy from its first appearance, 

 when it rivalled Venus at her brightest, down to its final 

 disappearance 16 months later. He repeatedly measured 

 its angular distance from the chief stars in Cassiopeia, 

 and applied a variety of methods to ascertain whether ic 

 had any perceptible parallax (chapter n., 43, 49). No 

 parallax could be definitely detected, and he deduced accord 

 ingly that the star must certainly be farther off than the moon ; 

 as moreover it had no share in the planetary motions, he 

 inferred that it must belong to the region of the fixed stars. 

 To us of to-day this result may appear fairly commonplace, 

 but most astronomers of the time held so firmly to Aristotle's 

 doctrine that the heavens generally, and the region of the 

 fixed stars in particular, were incorruptible and unchange- 



