Terrella, 1765. A terrella is a spherical
© Science Museum / Science & Society Picture Library
Terrella, 1765. A terrella is a spherical lodestone made of magnetite, a magnetic mineral. The word 'terrella', meaning little Earth, was given to spherical lodestones as they have the same magnetic properties as the Earth. This ornamental example was probably made by George Adams the elder (d 1773) of Fleet Street, instrument maker to the king. Height 180 mm, base diameter 95 mm, ball diameter 53 mm.