Greek, Moslem, and Chinese Design in the Mongol Scientific Instruments of A.D. 1279
More than fifty years ago a future president of the Royal Astronomical Society, J. L. E. Dreyer, drew attention to a remarkable Chinese anticipation of Tycho Brahe. Tycho's experiments towards a modern observatory technique led to the substitution of equatorial coordinates for the ecliptic reference frame on which early European measurement, following Graeco-Moslem practice, had been based. The ecliptic, or circle defined by the plane of our orbit round the sun, had been for the early pioneers so happy a hunting- ground for intriguing phenomena that they tended to choose it as a reference frame, ignoring the greater convenience of the plane of the earth's equator as providing a circle along which and from which to record stellar positions. Tycho ( 1546-1601) is generally supposed to have been the first to reverse this practice, and to mount his astronomical instruments in such a way as to utilise the equator as a circle of measurement. Instruments so mounted are therefore known as 'equatorials'. Most seventeenth-century designers in the pre-telescopic era of astronomical equipment constructed equatorials more or less Tychonic, with subsidiary circles for meridian and other work. In particular, the more obvious relics in Peking observatory had long been recognised as strictly Tychonic instruments copied from European designs and erected by Verbiest and other Jesuits about 1670. Dreyer's announcement was based on the researches of Wylie and of Yule, who investigated two large instruments, definitely equatorials, concealed near these European copies in Peking, and proved that these two owed nothing to Europe but were actually erected during the Mongol dynasty, probably in 1279.
A suggestion that the Chinese, most obstinately conservative of early scientists, were here ahead of the world, is sufficiently novel