206 THE GREEK ASTRONOMY. 



mus affixas." There is nothing inherently impro- 

 bable in this tradition, but we may observe, with 

 Delambre 2 , that we are not informed whether this 

 new star remained in the sky, or soon disappeared 

 again. Ptolemy makes no mention of the star or 

 the story ; and his catalogue contains no bright star 

 which is not found in the " Catasterisms" of Eratos- 

 thenes. These Catasterisms were an enumeration 

 of 475 of the principal stars, according to the con- 

 stellations in which they are ; and were published 

 about sixty years before Hipparchus. 



2. Constant Length of Years. Hipparchus 

 also attempted to ascertain whether successive 

 years are all of the same length ; and though, with 

 his scrupulous love of accuracy 3 , he does not ap- 

 pear to have thought himself justified in asserting 

 that the years were always exactly equal, he showed, 

 both by observations of the time when the sun 

 passed the equinoxes, and by eclipses, that the 

 difference of successive years, if there were any 

 difference, must be extremely slight. The obser- 

 vations of succeeding astronomers, and especially 

 of Ptolemy, confirmed this opinion, and proved, 

 with certainty, that there is no progressive increase 

 or diminution in the duration of the year. 



3. Constant Length of Days. Equation of 

 Time. The equality of days was more difficult to 

 ascertain than that of years ; for the year is mea- 

 sured, as on a natural scale, by the number of 



2 A. A. i. 290. 3 Ptolem. Synt. iii. 2. 



