142 THE GREEK ASTRONOMY. 



of eclipses, at considerable intervals of time from 

 each other ; for eclipses are very noticeable phe- 

 nomena, and must have been very soon observed 

 to occur only at new and full moon 83 . 



The exact length of a certain number of months 

 being thus known, the discovery of a cycle which 

 should regulate the calendar with sufficient accu- 

 racy, would be a business of arithmetical skill, and 

 would depend, in part, on the existing knowledge 

 of arithmetical methods ; but in making the dis- 

 covery, a natural arithmetical .sagacity was pro- 

 bably more efficacious than method. It is very 

 possible that the Cycle of Meton is correct more 

 nearly than its author was aware, and more nearly 

 than he could ascertain from any evidence and 

 calculation known to him. It is so exact that it 

 is still used in calculating the new moon for the 

 time of Easter; and the Golden Number, which 

 is spoken of in stating such rules, is the number 

 of this Cycle corresponding to the current year 84 . 



Meton's Cycle was corrected a hundred years 

 later (330 B. c.), by Calippus, who discovered the 



23 Thucyd. vii. 50. 'H a-eXtjvt] eicAeiTrer ervy^ave yap iravtre- 

 \t}vo<; ov<ra. iv. 52. Tow ij\iow 6K\j7rc'e rt eyevero irep\ vov- 

 /jirfviav. ii. 28. Noujuji/<a Kara creXrjvtjv (jacnrep xai /JLOVOV cone? 

 elvat ytyvevQat ^warou) o tj\io<: e^eXtire jueTCt weo-tjju (3 piav na\ iraXiv 

 av eir\t]ptadr], yei/o/xei/o? /jnji/oeiSj? KCU da-Tepcav TJI/WI/ eK(f>avevT(av. 



24 The same cycle of 19 years has been used by the Chinese 

 for a very great length of time ; their civil year consisting, like 

 that of the Greeks, of months of 29 and 30 days. 



The Siamese also have this period. (Astron. Lib. IT. K.) 





