140 A Short History of Astronomy tCa. V. 



interesting account of his chief discoveries. About the 

 same time he circulated manuscript copies of a catalogue 

 of 1,000 fixed stars, of which only 777 had been properly 

 observed, the rest having been added hurriedly to make 

 up the traditional number. The catalogue and the 

 Mechanica were both intended largely as evidence of his 

 astronomical eminence, and were sent to various influential 

 persons. Negotiations went on both with the Emperor 

 and with the Prince of Orange, and after another year spent 

 in various parts of Germany, Tycho definitely accepted an 

 invitation of the Emperor and arrived at Prague in June 



1 08. It was soon agreed that he should inhabit the 

 castle of Benatek, some twenty miles from Prague, where he 

 accordingly settled with his family and smaller instruments 

 towards the end of 1599. He at once started observing, 

 sent one of his sons to Hveen for his larger instruments, 

 and began looking about for assistants. He secured one of 

 the most able of his old assistants, and by good fortune 

 was also able to attract a far greater man, John Kepler, to 

 whose skilful use of the materials collected by Tycho the 

 latter owes no inconsiderable part of his great reputation. 

 Kepler, whose life and work will be dealt with at 

 length in chapter VIL, had recently published his first 

 important work, the Mysterium Cosmographicum ( 136), 

 which had attracted the attention of Tycho among others, 

 and was beginning to find his position at Gratz in Styria 

 uncomfortable on account of impending religious disputes. 

 After some hesitation he joined Tycho at Benatek early 

 in 1600. He was soon set to work at the study of Mars 

 for the planetary tables which Tycho was then preparing, 

 and thus acquired special familiarity with the observations 

 of this planet which Tycho had accumulated. The re- 

 lations of the two astronomers were not altogether happy, 

 Kepler being then as always anxious about money matters, 

 and the disturbed state of the country rendering it 

 difficult for Tycho to get payment from the Emperor. 

 Consequently Kepler very soon left Benatek and returned 

 to Prague, where he definitely settled after a short visit 

 to Gratz; Tycho also moved there towards the end of 

 1600, and they then worked together harmoniously for 



