Orreries are mechanical attempts to display the layout of the heavens. They illustrate the relative positions & motions of the planets & moons in the solar system, relative to the sun in the centre. The models were driven by clockwork, but were not normally to scale. The earliest orreries carried the moving bodies on a thin plate, while later models followed the 1764 design by Benjamin Martin, with the planets carried on radial arms. This design made it difficult to make the planets revolve & for their moons to revolve around them.
|Armilllary Sphere Orrery|
The first modern orrery was built in 1704 by George Graham & Thomas Tompion. This first model was copied by John Rowley of London for Prince Eugene of Savoy. Rowley was also commissioned to make a copy for his patron Charles Boyle the 4th Earl of Orrery (after whom the devices are named). An orrery & armillary sphere owned by the 4th Earl of Orrery is on loan to the Museum of the History of Science in Oxford. The museum's collection of orreries & armillary spheres is held in its historic building in Broad Street, Oxford.