THE USE OF THE CHART.

This chart is intended to represent approximately the aspect of the principal zodiacal stars as seen above the horizon of any place in central China, at any hour of any day, about the year B.C. 2300.

In order to apply the chart to a practical purpose, the reader is advised to cut out a sheet of paper (cardboard is preferable) with its upper edge exactly fitting the curved line A B O C D, and to draw, near to the bottom of the paper, a line coinciding with 'the hour-line' on the chart.

This being done, if it be asked what will be the aspect of the heavens when the Sun sets at the Vernal Equinox, the reader is to move the line at the bottom of the cardboard along the horizontal 'hour-line' of the chart until the place of the Sun in the Ecliptic at the Vernal Equinox O just touches the curved top of the paper; then all the stars not covered over are above the horizon at the time of that sunset, viz. in this case Aldebaran, Sirius, Spica, &c.; the Pleiades are just setting, Regulus and α Hydræ are very near the meridian, β Centauri is on the point of rising, and α Serpentis is well up above the horizon. This exactly corresponds with that state of the heavens which Yâo, (alleged in the Chinese records to have flourished about B.C. 2300,) indicated to his astronomers (Hsî and Ho) would be the case, viz. that he would find the star (or the

p. 28

stellar division) Shun Hwo (corresponding, it is said, to α Hydræ) culminating at the time of sunset at the Vernal Equinox 1.

Again, if it be required to find what constellation it 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.

p. 29

p. 30

Click to enlarge
Chart of the Principal Stars, chiefly Zodiacal, for the Epoch B.C. 2300

Footnotes

28:1 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.