Su Song built a 40-foot clock tower nobody could rebuild
In 11th-century Kaifeng, Su Song crowned a water-driven tower with a rotating bronze armillary sphere turned by the oldest known endless chain drive. When the capital fell and the machine was carried south, engineers, including his own son, failed to reassemble it. The son suspected his father had deliberately left out crucial details.
Su Song, who lived from 1020 to 1101, was a Song dynasty statesman whose interests ran from astronomy and cartography to metallurgy, poetry and art collecting. Emperor Zhezong ordered the clock project in 1086. Su first tested a wooden pilot model, finished in 1088; bronze parts were cast by 1090 and the whole tower was complete by 1094. Its armillary sphere weighed perhaps 10 to 20 tons, a bronze celestial globe sat in the middle, and 133 mechanical figures emerged from little doors to ring bells, beat drums and show the hour. The escapement came from a design by the monk Yi Xing and Liang Lingzan in 725, but this was the first armillary sphere given a mechanical clock drive.
His treatise on the tower, the Xinyi Xiangfayao, was written in 1092 and printed in 1094 with 47 detailed illustrations. It also carried a star atlas in five maps, now the oldest surviving printed star charts. After the capital moved from Kaifeng in 1127, Emperor Gaozong asked Su's son Su Xie to build a replacement, and the team failed.
Diplomacy tested his candour. Sent to the Liao dynasty of the Khitan people in 1077, he found their calendar slightly more accurate than the Song one, and told the emperor so; officials of the astronomy bureau were fined and punished. The court later had him compile the history of Song and Liao relations, a work filling 200 volumes, and his mapmaking knowledge helped settle a heated border dispute.
In 1070 he led scholars editing the Bencao Tujing, an illustrated pharmacopoeia covering plants, animals and minerals. It noted the use of ephedrine, described realgar's deep red colour and pitted matrix, recorded where the Chinese mitten crab lived, and was the first Chinese drug treatise to describe flax. Li Shizhen later copied the work into his Ming dynasty Bencao Gangmu. At court Su kept clear of the feud between Sima Guang's Conservatives and Wang Anshi's Reformists, rising to Minister of Justice in 1086.
Source: Su Song
