■a 



144 REMJRKS on the 



be 2°, 12'*, about t6' greater than it is determined, by the 

 modern aftronoiny of Europe. This difference is very confi- 

 derable ; but we Ihall find that it is not to be afcribed wholly 

 to error, and that there was a time when the inequality in que- 

 flion was nearly of the magnitude here afligned to it. In the 

 other points of the fun's path, this inequality is diminifhed, 

 in proportion to the fine of the mean diftance from the apogee, 

 that is, nearly as in our own tables. The apogee is fuppofed 

 to be 80° advanced beyond the beginning of the zodiac, and 

 to retain always the fame pofition among the fixed ftars, or to 

 move forward at the fame rate with them f . Though this 

 fuppofition is not accurate, as the apogee gains upon the 

 ftars about 10" annually, it is much nearer the truth than the 

 fyftem of Ptolhmy, where the fun's apogee is fuppofed abfo- 

 lutely at reft, fo as continually to fall back among the fixed 

 ftars, by the whole quantity of the precefTion of the equi- 

 noxes :j;. 



12. In thefe tables, the motions of the moon are deduced, 

 by certain intercalations, from a period of nineteen years, 

 in which ftie makes nearly 235 revolutions ; and it is curious 

 to find at Siam, the knowledge of that cycle, of which the in- 

 vention was thought to do fo much honour to the Athenian 

 Aftronomer Meton, and which makes fo great a figure in our 



modern 



* The equation of the Tun, or what they call the chaiaa, is calculated in the Sia- 

 mefe tables only for every 15* of the malteiomme, or mean anomaly. Cassini, ubi 

 fupra, p. 2y9. 



+ Aft. Ind. p. 9. 



J The error, however, with re'peft to the apogee, is lefs than it appears to be j 

 for the motion of the Indian zodiac, being nearly 4' fwifter than the ftars, is but 6" 

 flower than the apogee. The velocity of the Indian zodiac is indeed neither the 

 fame with that of the flars, nor of the fun's apogee, but nearly a mean between 

 them. 



