Ferguson's orrery (planetary dial). This four-wheeled orrery shows the Earth and Moon (right) in relation to the Sun (upper centre). It was designed by the Scottish astronomer and instrument maker James Ferguson (1710-1776). Labels on the dial include month names and numbers, and names and symbols for the signs of the zodiac. The circular label at centre says: 'Place of the Node with the Golden Number and Dominical Letter'. The golden number relates to the lunar cycle, and the dominical letter to the cycle of years according to the days of the week. This artwork is from the October 1747 issue of The London Magazine.