Song I-yeong’s Armillary Clock

Also called: Honcheon sigye, Armillary Clock

An astronomical clock made under King Hyeonjong by Song I-yeong, driving an armillary sphere with weights and gears.

Song I-yeong of the Bureau of Astronomy made it in 1669. An armillary sphere showing the motions of the sun and moon sits in the middle, and the force of falling weights turns a gear train that strikes the hours and moves the sphere — joining the mechanism of the Western striking clock to the traditional East Asian armillary sphere.

In the same year Yi Min-cheol made a water-driven armillary sphere. Song’s clock is counted the most sophisticated surviving Joseon astronomical clock; it is a National Treasure in the Korea University Museum, and its armillary sphere appears on the back of the 10,000-won note.