magnetarium
/maɡnɪˈtɛːrɪəm/Now historical
noun
An instrument for illustrating the magnetism of the earth.
- The magnetarium consisted of two concentric globes between which was a spherical shell of wire gauze. Around the inner globe wire was coiled in planes at an angle of 23½ degrees to the equator; another wire was coiled in planes round the wire gauze. An electric current passed through both wires gave rise to a magnetic field round the outer globe resembling the earth's field..
Origin
Late 19th century; earliest use found in Youth's Companion. From magnet + -arium.