The armillary sphere (Fig. [117]) stands at the east end of the court. It is an instrument of huge dimensions being described in early records somewhat as follows, in each reference there being allusion to its beautiful workmanship, and to its design as possessing remarkable excellence. The supporting base of the piece has a mythological significance. The four dragons, which play such a part in the Chinese geomancy, are here represented as chained to the earth, while upholding the spheres. Its substantial horizon circle, crossed at right angles by a double ring representing an azimuth circle, forms the outer supporting framework. The upper surface of the horizon circle is divided into twelve equal parts, marked by the several Chinese cyclical characters applied to the twelve hours into which the day and night was divided. Around the outside of this horizon circle these twelve characters appear again, with the Chinese names for the several points of the compass. On the inside of this circle one finds the names of the twelve States into which the ancient Empire was divided, each State being thought of as under the influence of a particular quarter of the heavens.
Fig. 117. Ancient Mongolian Armillary Sphere, ca. 1274.
Inside this frame is placed an equatorial circle within which is a series of movable circles made to turn on polar pivots attached to the azimuth circle. These movable circles consist of an equatorial circle, a double ring ecliptic, an equinoctial colure, and a double ring solstitial colure. The equator is divided into twenty-eight unequal portions marked by the names of as many constellations of very ancient origin. The ecliptic is divided into twenty-four equal parts according with the divisions of the year. Within the circles just described there is a double revolving meridian with a double axis and within this a fixed tube for taking sights.
All the circles of this armillary sphere are divided into 365¼ degrees corresponding to the days of the year and each degree is divided into hundreds. At the corners of the base outside the dragons are four miniature rocks in bronze, with the respective inscriptions “Keen Shan,” northwest or celestial mountain; “Kwan Shan,” southwest or terrestrial mountain; “Seuen-Shan,” or southeast mountain; “Kan Shan,” northeast mountain.
When the astronomer Père Ferdinand Verbiest (1623-1688),[116] undertook the survey and management of mathematics for the Emperor he, like his predecessor Ko-Shun-King four hundred years before, began his task, as noted above, by ordering the removal of the old instruments from the observatory and the construction of new ones. Six of these are referred to in the records of the period as possessing especial merit, including a zodiacal armillary sphere six feet in diameter, an equinoctial armillary sphere six feet in diameter, a horizon azimuth likewise six feet in diameter, a quadrant having a radius of six feet, a sextant with a radius of eight feet, and a celestial globe having a diameter of six feet.
The armillary spheres have each but four circles, being of excellent workmanship, and having mountings of elaborate Chinese designs.
That which especially interests us here is the celestial globe (Fig. [117a]) which Le Compte describes somewhat in detail. “This in my Opinion,” he says, “is the fairest and best fashioned of all the Instruments. The Globe itself is brazen, exactly round and smooth; the Stars well made, and in their true places, and all Circles of proportional breadth and thickness. It is besides so well hung, that the least touch moves it, and tho’ it is above two thousand weight, the least Child may elevate it to any Degree. On its large concave Bases are placed opposite four Dragons, whose Hair standing up on end, support a noble Horizon commendable for its breadth, its several Ornaments, and the delicacy and niceness of the Work. The Meridian in which the Pole is fixed rests upon Clouds that issue out of the Bases, and slides easily between them, its Motion being facilitated by some hidden Wheels, and moves with it the whole Globe to give it the required Elevation. Besides which, the Horizon, Dragons and two brazen Beams, which lie cross in the Center of the Bases Concavity, are all moved at pleasure without stirring the Bases which still remain fixed; this facilitates the due placing of the Horizon, whether in respect of the Natural Horizon, or in respect of the Globe. I wonder how Men who live six thousand Leagues from us could go through such a piece of Work; and I must own, that if all the Circles which are divided, had been corrected by some of our Workmen, nothing could be more perfect in this kind.” This piece, it may be noted, was carried away to Potsdam at the close of the Boxer Rebellion, copies of them being left in the old observatory. The Treaty of Versailles directed that the originals should be returned to their early home.