stellar division) Shun Hwo (corresponding, it is said, to α Hydræ) culminating at the time of sunset at the Vernal Equinox.
Again, if it be required to find what constellation is culminating at the time of sunset at the Summer Solstice, the cardboard must be moved, as before, towards the right hand until the position of the Sun at the Summer Solstice, viz. G, just touches the horizon curve, when it will be seen that α Serpentis and Antares are then culminating, Regulus and β Centauri are just setting, while the constellations of Aquila and Aquarius are rising ; Vega is a conspicuous object above the eastern horizon. This again corresponds to the indications given by Yâo to his astronomers, viz. that they would find the constellation Scorpio culminating at the time.
Thirdly, to find what constellation is culminating at sunset at the Winter Solstice, the cardboard horizon is to be moved, as before, until the Sun at F falls upon it, when the constellations Aries and Taurus with the Pleiades will be seen near to their culmination. This is a third correspondence with the indications of the astronomical sovereign.
Lastly, at sunset of the Autumnal Equinox the movable horizon is to be shifted to the left until the point A falls upon it, where it will be seen in this position that the stars in Aquarius are culminating at the time. It is scarcely possible that all these indications of the positions of the stars at these several times of the year could be simultaneously correct at any other epoch than somewhere about B.C. 2300 or a very small number of centuries before or after.
The reader may easily make for himself many other interesting applications of the chart. A general notion of the effects of precession on the positions of the stars may be seen at once by observing the three positions of the Pleiades, at the three epochs B.C. 2300, A.D. 1, and A.D. 1878, marked in the chart by the letters K, L, M ; and as the approximate effect of precession is to cause all stars to move parallel to the Ecliptic and through the same arc, if the reader will imagine every star to be shifted parallel to the Ecliptic through spaces equal respectively to K L, L M, he will get the aspect of the heavens at the epochs A.D. 1 and A.D. 1878.
The following table has been calculated for the apparent positions of the principal stars in the years B.C. 2300, B.C. 1500, A.D. 1, and A.D. 1000 ; except in one instance it will be found to confirm a similar calculation made by Biot for the earliest of these dates.
- See an excellent memoir by Mr. Williams, the late Assistant Secretary of the Royal Astronomical Society, on Chinese Comets, procurable at the apartments of the Royal Astronomical Society, Burlington House, London.