194 -A Short History of Astronomy [CH. vil. 



147. Meanwhile Kepler's position at Linz had become 

 more and more uncomfortable, owing to the rising tide 

 of the religious and political disturbances which finally 

 led to the outbreak of the Thirty Years' War in 1618 ; but 

 notwithstanding this he had refused in 1617 an offer of 

 a chair of mathematics at Bologna, partly through attach- 

 ment to his native country and partly through a well-founded 

 distrust of the Papal party in Italy. Three years afterwards 

 he rejected also the overtures made by the English 

 ambassador, with a view to securing him as an ornament 

 to the court of James L, one of his chief grounds for refusal 

 in this case being a doubt whether he would not suffer 

 from being cooped up within the limits of an island. 

 In 1619 the Emperor Matthias died, and was succeeded 

 by Ferdinand II., who as Archduke had started the perse- 

 cution of the Protestants at Gratz ( 137) and who had 

 few scientific interests. Kepler was, however, after some 

 delay, confirmed in his appointment as Imperial Mathe- 

 matician. In 1620 Linz was occupied by the Imperialist 

 troops, and by 1626 the oppression of the Protestants by 

 the Roman Catholics had gone so far that Kepler made 

 up his mind to leave, and, after sending his family to 

 Regensburg, went himself to Ulm. 



148. At Ulm Kepler published his last great work. 

 For more than a quarter of a century he had been 

 steadily working out in detail, on the basis of Tycho's 

 observations and of his own theories, the motions of the 

 heavenly bodies, expressing the results in such convenient 

 tabular form that the determination of the place of any 

 body at any required time, as well as the investigation 

 of other astronomical events such as eclipses, became 

 merely a matter of calculation according to fixed rules ; 

 this great undertaking, in some sense the summing up of 

 his own and of Tycho's work, was finally published in 1627 

 as the Rudolphine Tables (the name being given in honour 

 of his former patron), and remained for something like 

 a century the standard astronomical tables. 



It had long been Kepler's intention, after finishing the 

 tables, to write a complete treatise on astronomy, to be 

 called the New Almagest', but this scheme was never fairly 

 started, much less carried out. 



