THE NEW COSMOLOGY 



Tubingen, where he came under the influence of the 

 celebrated Maestlin and became his life-long friend. 



Curiously enough, it is recorded that at first Kepler 

 had no taste for astronomy or for mathematics. But 

 the doors of the ministry being presently barred to 

 him, he turned with enthusiasm to the study of as- 

 tronomy, being from the first an ardent advocate of the 

 Copernican system. His teacher, Maestlin, accepted 

 the same doctrine, though he was obliged, for theologi- 

 cal reasons, to teach the Ptolemaic system, as also to 

 oppose the Gregorian reform of the calendar. 



The Gregorian calendar, it should be explained, is 

 so called because it was instituted by Pope Gregory 

 XII I. , who put it into effect in the year 1582, up to 

 which time the so-called Julian calendar, as introduced 

 by Julius Caesar, had been everywhere accepted in 

 Christendom. This Julian calendar, as we have seen, 

 was a great improvement on preceding ones, but still 

 lacked something of perfection inasmuch as its theo- 

 retical day differed appreciably from the actual day. 

 In the course of fifteen hundred years, since the time 

 of Caesar, this defect amounted to a discrepancy of 

 about eleven days. Pope Gregory proposed to correct 

 this by omitting ten days from the calendar, which was 

 done in September, 1582. To prevent similar inac- 

 curacies in the future, the Gregorian calendar provided 

 that once in four centuries the additional day to make 

 a leap-year should be omitted, the date selected for 

 such omission being the last year of every fourth 

 century. Thus the years 1500, 1900, and 2300, A.D., 

 would not be leap-years. By this arrangement an 

 approximate rectification of the calendar was effect- 



