[ 41 ] Both the Súrye-Siddhảnta and the Siddhanta-Siromaại, the standard Siddhántas at present in use, give a rule to test the amount of ayanánsa by observation. It consists in subtracting from 12 signs the longitude of the sun computed after the Siddhántas for the moment when the sun crosses the vernal equinoctial point. Thus, on the 13th April 1894, the sun's longitude for Greenwich mean noon was 23° 32' 7", while an almanac gives us 1' 21' 25" as the sun's longitude for the same instant, making the ayanámsa 22° 10'37". It will be seen there- fore that notwithstanding the higher precessional rate of the Súrya Siddh&nta, the calculated amount becomes less than the actual by nearly 1° 16', while the Grahalaghava makes it greater by about 39: To come to the second method, viz. to find the true longitude of the initial point as defined by stars. All the modern Siddhántas agree in the statement that the longitudes of all heavenly bodies are to be measured from the Star Revati situated on the ecliptic. The star has been identified with & Piscium. Now, this is a star of the fifth magnitude and is barely visible to the naked eye. The question is, why was this particular star out of the many situated on the ecliptic,—some of which are larger, ---chosen for marking the beginning of the zodiac? The answer has been--and there is no doubt about the accuracy of the answer—that the vernal equinox happened near the star when the present system of astronomical measurement came into vogue. So far it is plain sailing. For, we can easily find the longi- tude of the star from the vernal equinoctial point and at once Digitized by Google
