A NEW ASTRONOMY 195 



him, after medical study at Cracow, first to the university of 

 Vienna, then to the chief Italian universities, Bologna, Padua, 

 Ferrara, and Rome, where he found opportunity to cultivate his 

 mathematical talents and to master what was then known of 

 astronomy. He became canon at Frauenburg in his native land 

 in 1497, and from 1512 until his death thirty years later, was 

 settled there, rendering varied public services, and practising 

 gratuitously, as needful, the medical art he had also learned. At 

 the same time he found it possible to devote much attention to 

 astronomical studies. 



In his study of the classical writers he came upon a statement 

 that certain Pythagorean philosophers explained the phenomena 

 of the daily and yearly motions of the heavenly bodies by sup- 

 posing the earth itself to rotate on its axis and to have also an 

 orbital motion. 



' Occasioned by this, I also began to think of a motion of the earth, 

 and although the idea seemed absurd, still, as others before me had 

 been permitted to assume certain circles in order to explain the motions 

 of the stars, I believed it would readily be permitted me to try whether 

 on the assumption of some motion of the earth better explanations 

 of the revolutions of the heavenly spheres might not be found. And 

 thus I have, assuming the motions which I in the following work at- 

 tribute to the earth, after long and careful investigation, finally found 

 that when the motions of the other planets are referred to the circu- 

 lation of the earth and are computed for the revolution of each star, 

 not only do the phenomena necessarily follow therefrom, but the 

 order and magnitude of the stars and all their orbs and the heaven 

 itself are so connected that in no part can anything be transposed 

 without confusion to the rest and to the whole universe.' Dreyer. 



' I made every effort to read anew all the books of philosophers I 

 could obtain, in order to ascertain if there were not some one of 

 them of the opinion that other motions of the heavenly bodies existed 

 than are assumed by those who teach mathematical sciences in the 

 schools. So I found first hi Cicero that Hicetas of Syracuse believed 

 the earth moved. Afterwards I found also in Plutarch that others 

 were likewise of this opinion. . . . Starting thence I began to re- 

 flect on the mobility of the earth.' Timer ding. 



