18 Remarks on Ancient Eclipses. 



1 . The lunar cycle among the Chaldeans was called the saros 

 and sara, from ^i^HD, sahurci, the moon. This cycle it is said 

 contained two hundred and twenty-three synodical months, or 

 eighteen Julian years, ten days, when the same cvcle or period 

 contains five leap days, and eleven days when it contains four leap 

 days, seven hours, forty-eight minutes, and one-fourth ; in which 

 time all the corresponding new and full moons and eclipses re- 

 turn again. 



2. The principal alteration of the time of the day in all 

 eclipses depended on the e>;cess of this period above an even 

 number of days, which is computed at seven hours, forty-three 

 minutes, and one-fourth ; so that the cycle put every corre- 

 sponding eclipse later than the foregoing almost eight hours; 

 and three of those cycles amounted to fifty-four years and thirty- 

 three or thirty-four days, which a single cycle could not do. 



'S. There are reckoned nine hundred years from the time that 

 the moon begins to enter the ecliptic limit for eclipses of the 

 moon on one side, till it goes out of it on the other ; in all which 

 time there will be fifty periods, and eclipses of the moon in each 

 period : and there are reckoned to elapse twelve hundred and 

 sixty years from the time that the moon begins to enter the ecliptic 

 limit for eclipses of the sun on one side the node, till it goes out 

 of it on the other^ during which long time there will be seventy 

 periods, and somewhere eclipses of the sun in each period, after 

 which there will be no such eclipses for many centuries. 



4. The Chaldean saros was improved by Meton, who first dis- 

 covered, that in the course of nineteen years the new and full 

 moons returned to the same days of the month, when a nevv- cycle 

 began ; on which account it was called by the Greeks Emieade- 

 caeteris, or cycle of nineteen years : in which time it was thought 

 two hundred and tliirty-five lunations were exactly completed, 

 comprehending one hundred and ten new, and one hundred and 

 twenty-five full moons. 



5. The Metonic period being found defective in the time of 

 Calippus, and one-fourth part of a day too much, the said Ca- 

 lippus added four whole periods of nineteen years, and instituted 

 the cycle of seventy-six years, at the expiration of which he took 

 off one day ; and this was supposed a perfect correction of the 

 lunar account nnti, its further revision by Hipparchus. 



(). Uipparchus having demonstrated the imperfection of the 

 Calippic pericd by one v.hole day too much in four such periods, 

 determined on a new period oT three hunched and four years, when 

 he deducted one day. The period of Calippus began in the 

 summer of the same year that Alexander con(|uered Darius in 

 the famous battle of Arbela, which was the third year of the 

 112th Olympiad, as proved from Ptolemy in \\\s Almagest, lib. 7, 



cap. 



