The mean rate of Equinoctial Precession for the past eighteen centuries being 50·1´´ per year, we must divide 21° 52´ by this amount of precession to obtain the year of coincidence. The result is 1571 years, which, being taken from the present year 1912, gives the year A.D. 341 as that in which the two zodiacs coincided. But by taking the actual precession for 1912 and the increment for t years where t equals 1571 - 62, or 1509 years, we have the actual precession as equal to 50´´ per year nearly, and 21° 52´ divided by 50´´ is 1574, the years to be taken from 1912, which gives the year A.D. 338. According to our estimate of the rate of precession, therefore, the Epoch will vary between A.D. 338 and 341. In round numbers, therefore, we may regard the year A.D. 340 as that of the coincidence of the zodiacs, and the number of years since elapsed multiplied by the mean rate of 50·1´´ will give the increment known as Ayanámsha for any date since the Epoch.
But I find an entry in the Ephemeris of Kumbakonam to this effect.
“Mean amount of precession at commencement of K.Y. 5014 (A.D. 1912), 22° 27´ 20´´. Rate of precession, 50·26´´.”
Now if we divide the above amount of precession by the rate we shall get 1612 years, which would give the Epoch A.D. 300, whereas, as we have seen, other data in the Ephemeris lead us to the year A.D. 340. Now I have checked the Kumbakonam Ephemeris, and find that so far as the Solar ingresses are concerned they agree with the Nautical Almanac, and there would therefore appear to be no reasonable doubt that if the true amount of precession is here given, the true Epoch for the coincidence of the zodiacs has been found. But I am advised by Dr. V. V. Ramanan that there is an increment not generally recognized by either the Indian or European astronomers, but which is nevertheless an essential part of the calculation. It is that of the progression of the asterisms or constellations from west to east, along the order of the signs at the rate of 8´´ per year, to which I have already referred in an extract from one of his valuable letters. If, therefore, we add this 8´´ to the annual precession 50·1´´, we shall have 58·1´´ as the total precession of the Equinoxes on the first point of As’wini, and then if we further divide the amount of precession for the year 1912 as given in the Panchángam, namely, 22° 27´ 20´´ by 58·1´´, we shall get 1390 years, which taken from 1912 yields the year of coincidence A.D. 521.
From various sources, therefore, we have the years A.D. 300, 306, 338, 527, 528 and 521. The former dates take account only of the precession of the Equinoxes on a fixed zodiac, whereas the latter take into account also a direct motion of this so-called “fixed” zodiac which amounts to 8´´ per year, and which has to be applied to the precession. It is further to be observed that the Epochs 338 and 306, variously derived above, are unified by the adoption of 58·1´´ as the total annual precession of the Equinoxes on the first point of As’wini. It needs but quotation of authority for this increment of 8´´ in order to establish the date of zodiacal coincidence beyond disputation, at all events within the limits of a very few years.
The above questions have an historical interest. Varahamihira, who mentions the coincidence of the solstices with the cardinal constellations Makaram and Katakam as having taken place in his day, has not been finally placed by the chronologists. Astronomical notes made by him have chiefly been used for this purpose, and the writing of his book the Brihat-samhita, in which the above note occurs, is on these grounds fixed at A.D. 505.
But then we have to remember that Mihira speaks only in general terms when he refers to the coincidence of the zodiacs. He had no instruments which would have enabled him to make a close observation, but he could make certain approximations from the meridian transit of some of the chief stars in the constellations. We have no reason, therefore, to expect more than an approximate agreement of the date of Mihira with that of the true coincidence of the zodiacs. The Graha Laghava, which is in general use in India, gives this latter as A.D. 522 or 444 Shaka.
The Shaka Epoch is known to be A.D. 78. Dr. V. V. Ramanan gives reasons for accepting the year A.D. 525. In the present state of the controversy I see no reason against this Epoch.
CHAPTER XXIII
LUNAR INFLUENCE
The average notion of the Moon’s action is that it affects the tides and lunatics. Beyond this the popular encyclopedia does not go, and the average man himself is not observant of anything in Nature except the way of his fellow-man.