88 A Short History of Astronomy [CH. in. 



turned his attention from Greek to fighting, and Regiomon- 

 tanus moved once more, settling this time in Niirnberg, then 

 one of the most flourishing cities in Germany, a special 

 attraction of which was that one of the early printing 

 presses was established there. The Niirnberg citizens 

 received Regiomontanus with great honour, and one rich 

 man in particular, Bernard Walther (1430-1504), not only 

 supplied him with funds, but, though an older man, became 

 his pupil and worked with him. The skilled artisans of 

 Niirnberg were employed in constructing astronomical 

 instruments of an accuracy hitherto unknown in Europe, 

 though probably still inferior to those of Nassir Eddin and 

 Ulugh Begh ( 62, 63). A number of observations were ( 

 made, among the most interesting being those of the comet j 

 of 1472, the first comet which appears to have been; 

 regarded as a subject for scientific study rather than for 

 superstitious terror. Regiomontanus recognised at once the 

 importance for his work of the new invention of printing, 

 and, finding probably that the existing presses were unable 

 to meet the special requirements of astronomy, started a 

 printing press of his own. Here he brought out in 1472. 

 or 1473 an edition of Purbach's book on planetary theory,) 

 which soon became popular and was frequently reprinted. ' 

 This book indicates clearly the discrepancy already being \ 

 felt between the views of Aristotle and those of Ptolemy. 

 Aristotle's original view was that sun, moon, the five 

 planets, and the fixed stars were attached respectively to 

 eight spheres, one inside the other ; and that the outer 

 one, which contained the fixed stars, by its revolution was 

 the primary cause of the apparent daily motion of all the 

 celestial bodies. The discovery of precession required on 

 'the part of those who carried on the Aristotelian tradition 

 the addition of another sphere. According to this scheme, 

 which was probably due to some of the translators or 

 commentators at Bagdad ( 56), the fixed stars were on 

 a sphere, often called the firmament, and outside this was 

 a ninth sphere, known as the primum mobile, which moved 

 all the others ; another sphere was added by Tabit ben 

 Korra to account for trepidation ( 58), and accepted by 

 Alfonso and his school ; an eleventh sphere was added 

 towards the end of the Middle Ages to account for the 



