The Astronomical Observatory of Pekin

Abstract

IN the course of a lecture delivered before the Pekin Literary Society, on the Astronomical Observatory of the Chinese capital, Prof. Russell said that it is the oldest in the world. The eldest in Europe is that of Denmark, founded in 1576 by Frederick III., at which Tycho Brahé made his famous observations. The Royal Observatory at Paris was not opened till 1671, and that of Greenwich three years later. The Pekin Observatory was established in 1279, in the reign of Kublai Khan, the first emperor of the Mongol dynasty, and three of the original instruments yet remain. In 1378, these instruments were probably used in observing Halley's comet, and they will be used twenty-two years hence to witness its next return. If the visitor enters by a door in the south wall of the Observatory, he comes into a court running east and west. In this court are kept the three original instruments. There were four at one time, but the fourth, a celestial globe, has disappeared. Kuo Shouching, a Chinese astronomer, who flourished in the reign of Kublai Khan, was the maker of these. Before their construction, bronze astronomical instruments, which were made about the year 1050, were used, first at K'ai Fêng Fu, the capital of Honan, whence they were removed to Pekin. Kuo Shouching found these worn out by age, and otherwise unsuitable, as the height of the Pole differed by 4°; and so he constructed four instruments, of which three now remain. In the east end of the court is the equatorial armillary, which is made of bronze, and consists of (1) a massive horizontal circle, held up at four corners by four dragons, each of which with one upraised palm supports the bronze circle, while round the other palm a chain is passed and fastened behind to a small bronze pillar,—the dragons are themselves works of art; (2) a double vertical circle firmly connected with the horizontal circle at its north and south points, and supported at its lowest point by a bronze pillar. On the vertical circle, which, like the other, is fixed, at a distance equal to the latitude of Pekin, that is 40°, are two pivots corresponding to the North and South Poles. Revolving round these pivots are two circles, one double, corresponding to the solstitial colore—that is, the great circle passing through the Poles and the solstices; the other single, corresponding to the equinoctial solure—that is, the great circle through the Poles and the equinoxes. Half-way between the Poles is another circle, which corresponds to the equator, the rim of which is let into the two colure circles. There is also another circle, making with the latter an angle of 23½, and corresponding to the ecliptic. Finally, inside these circles, all of which revolve together round the polar axis, there is another double circle, representing the polar circle or declination, and between the rims of this double circle revolves the hollow tube through which observations were made. It is probable that there were originally threads across the tube to deüne the line of sight. There are in the circles 365¼°—that is, a degree for each day in the year—and each degree is subdivided into divisions of 10′ each. When using this instrument the observer turned round the inner circle till the heavenly body was sighted in the centre of the tube, and then the distance of the star was read from the Pole on the polar circle, and its position on the equator by the equatorial circle. The complex construction was in some particulars of no use whatever: the ecliptic and one of the colures were useless. At the west end of the court are the other two instruments, the equatorial, or astrolabe, and the altitude and azimuth instrument. The former is remarkably simple in its construction. There is a fixed bronze circle placed parallel to the equator, and there is another double circle perpendicular to it, which moves round an axis passing through the centre of and perpendicular to the equatorial circle. Of course there is also the hollow tube for observation. This instrument is free from the clumsiness and complexity of the first-named instrument, and in the form of its mounting much more closely resembles those in use at present in all Observatories than the other instruments. The altitude and azimuth instrument consists of two circles, one horizontal and fixed, the other vertical and movable round an axis passing through