Diptych dial. This dial consists of two leaves that fold together when not in use. Leaf Ia displays a lunar volvelle marked with Chinese characters. Leaf Ib contains a vertical dial. Leaf IIa features the horizontal dial, in the centre of which is a compass with the cardinal points marked in black around it (red for South). A red string gnomon is attached between the two leaves.

Leaf IIb gives instructions for use in Chinese characters - 'The method of use of this sundial: pick up and open to the right angle. Direct the compass needle to the South, observe the string's shadow and find the time exactly'. This is followed by the instructions for the volvelle: 'Moon dial: pull the brass pin out and put it in the seasonal hole along the side. Then point the character 'horse' [i.e. the pointer on the disc] of the rotating dial to the day of the month on the surface. Put another needle into the centre of the dial and look at the shadow of the needle to find the time. The time will have no error'. This is followed by the signature, 'Xin-An, Xiu-Li, Wang Yang-Qi' (district followed by town, followed by maker's name). The sides of the leaf carry 26 characters giving the seasons of the year from solstice to solstice and back.

This diptych dial is typical of those instruments being made during the late 19th century, showing the influence of the West on Chinese styles.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.