2 * TRUE LONGITUDES OF THE PLANETS [CH. II no change in the rate of motion because (the current Rsine- difference being fixed throughout that element) the Rsine- difference does not decrease or increase : when viewed in this way, this jhabhukti is defective. Rule 9-10 shows that so long as the Sun remains in the same element- ary arc (measuring 225') the Sun's jlvabhukti does not vary. Since the Sun remains in the same element for three consecutive days, its jhabhukti remains the same for three consecutive days. This is defective, because the rate of motion varies from instant to instant. 1 Similarly, so long as the Moon remains in the same elementary arc, its velocity remains the same because throughout that element the Rsine-diffe- rence is constant. Thus, in the case of the Moon, the instantaneous daily motion obtained with the help of the Moon's current Rsine-difference is defective. Author's opinion regarding the true daily motion : 15 (iij. The karnabhukti* or the difference between the true (longitudes) for two consecutive days is the true (daily) motion. The commentator Paramesvara thinks that the karnabhukti is the instan- taneous daily motion. . The comparative merits and demerits of the jhabhukti and the karnabhukti have been examined in detail by Mlakantha in his commentary on i,ii.22-25. A rule for finding the Sun's declination with the help of the Sun's tropical (sayana) longitude : 16. 1397 is (in minutes of arc) the Rsine of the (Sun's) greatest declination. The product of that and the Rsine of the bhuja due to the Sun's true (tropical) longitude divided by the radius is the Rsine of (the Sun's) desired declination. 3 1 Instantaneous change of velocity was recognised by the Hindu astro- nomer Manjula (932) who, on the basis of the idea of the "infinitesimal increment", gave a rule for the instantaneous velocity of a planet. 9 See stanza 8 above. » Cf. MBh, iii. 6(i).
