Armillary sphere, 1731.
© Science Museum / Science & Society Picture Library
This sphere was made by Jonathan Sison for Frederick, Prince of Wales, father of the future George III. It is Copernican, having the Sun at the centre. The Earth, Moon and other planets can rotate about the Sun. The horizontal outer ring is engraved with the calendar, the signs of the zodiac, and the points of the compas. The signs of the zodiac are shown eleven days earlier than at present owing to the changing of the calendar in 1752.