ON THE EQUINOXES. 235 



ponds in time to a revolution of the Sun % and the exeentrick de- 

 ferent anfwcrs to the true revolution ©f the planet m it$ orbit) 



So far the Indian fyftem* as already remarked by Mr. Davis In 

 his treatife on the aftronomieal computations of the Hindus* egrets 

 with the Ptolemaich At the firft glance It will remind the reader of 

 the hypothefis of an esceotrick orbit devifed by Buppaeck us ? sod of 

 that of an epicycle on a deferent, faid to hafse been" Invented by 

 Apollonius but applied by HiPPARessus. At the fame time the 

 ontiffion of an equant (having doable tfie eccentricity of the deferent) 

 imagined by Ptolemy for the five minor planets, as well as the 

 epicycle with a deferent of the centre of the exeentrick, contrived by 

 him to account for the eve&ion ©f the Moon; and the circle of ano~ 

 maly of excentricity, adapted t© the inequality ©f Mercury's mo* 

 tions, cannot fail to attraft notice,, 



The Hindus, who have not any of Ptolemy's additions to the theory 

 of Hipparchusj have introduced a different modification of the hypo- 

 thefis, for they give an oval form to the excentrick or equivalent 

 epicycle,, as well as to the planets proper epicycle. That is, they af- 

 fume the axis of the epicycle greater at the end of the (Jama) even 

 quadrants of anomaly (or 9 in the line of the apfides and conjunctions j 

 and leail at the end of the (vijhama) or odd quadrants ( ift and 3d! 

 and intermediately in proportionf. This contrivance of an oval epi- 



* At. Res. vol. 2. p. 2 jo. 



+ Rad: Sine of Anomaly ;: Diff. between circlei defcribed os greater! and leaft axii : diff". between cir- 

 clet defcribed on greateft axi» and ©n the diameter of the epicycle for the propofed anomaly. Whence the 

 circle defcribed on that diameter is determined ; and it ttfed for the epicycle in compuiaiioni for that ano- 

 maly. Since circle* arc to each other m their Radii, the proportion abore ftated anfwcti to the following j 



