358 Chaldean Periods. 



By subtracting 1 1 years from the above sum, we shall very 

 nearly bring it to the Magnus Annus of the ancients, or 600 years, 

 when they supposed the motions of the sun and moon to be 

 completed, according to Josephus*; for in 11 years the moon 

 returns to the sun within about 10 degrees, or less than one day. 

 It was by the aid oi this great period of 600 years that Hip- 

 parchus extended his science in calculating Ephemerides of the 

 sun and moon as he is related to have done, and that with suf- 

 ficient exactness for the regulating of their calendar. 



* Praeterea turn propter studium virtutis, turn propter utilitatem inven- 

 tai-um artium, ut astronomite, ac geomctria?, Deus illis prolixiorem largitus 

 est vitain: quarum certitudiiiem asscqui non potcrant, si minus DC annii 

 vixiascnt, ex tot cnim Magnus Annus constat. Lib. 1. cap. 4. 



