10 MEAN LONGITUDES OF THE PLANETS of the day (without the application of the longitude correction) (gives the longitude correction for the Sun). But that is not so, as to the east and west of a place on the prime meridian (i.e., on the same parallel of latitude) the latitude (and therefore the shadow of the gnomon) remains the same. 1 This rule has also been criticised by Srlpati, who says : "Whatever is obtained here as the difference between the longitudes of the Sun derived from the midday shadow (of the gnomon) and that obtained by calculation (for midday, without the application of the longitud&correc- tion) when multiplied by the (local) circumference of the Earth and divided by the (Sun's daily) motion gives the yojanas of the longitude (i.e., the distance xxyojanas of the local place from the prime meridian). This is gross on account of the small change in the Sun's declination." 2 The reader will also note that the longitude derived from the midday shadow will be tropical, whereas the other is not. A rule for the longitude in time : 29. The difference between the computed and observed times of an eclipse is the longitude in terms of time. 3 The computed time is the local time for the place lying at the intersection of the prime meridian and the local circle of latitude, while the observed time is the local time for the local place. The difference between the two is obvi- ously the longitude in time for the local place. It may be pointed out that in Hindu astronomy time is measured from sunrise. Criterion for knowing whether the local place is to the east or to the west of the prime meridian : 30. If the (lunar and solar) eclipses occur after the calcula- ted time, then the observer is to the east of the prime meridian ; otherwise, to the west. 4 The calculated time is the local time for the place lying at the intersec- ti on of the prime merid ian and the local circle of latitude. 1 Cf. MBh. ii. 6. 2 SiSe, ii. 103. » Cf. MBh. ii. 7.
- Cf. MBh, ii. 9.