Purple Mountain Observatory
Nanjing, Jiangsu, PRC

19. Gnomon

This is one of China's most ancient astronomical instruments. The meridian horizontal plate with the scale on it is called qui and the higher vertical pillar is called biao. The number of days in a tropical year and the 24 divisions of the solar year can be determined by the shadow of the biao at noon. It was made in 1436, the 4th year of the Zheng-Tong Reign of the Ming Dynasty.