Tellurions

Part of speech: noun

Definitions

1. Devices that mechanically demonstrate how the Earth rotates on its axis and revolves around the Sun, often showing the seasons and eclipses
2. Mechanical models of the Earth and its orbit that use gears to show the planet's daily spin and yearly path around the Sun
3. Instruments built to illustrate the motions of Earth in relation to the Sun and Moon, typically with a globe mounted on a rotating arm

Etymology: The tellurion is a mechanical model of the Earth and Moon orbiting the Sun, and its name was coined in 1766 by Benjamin Martin, an English lecturer, lexicographer and maker of scientific instruments. Martin built his name from Latin "tellus", meaning earth or ground, and tacked on the suffix "-ion", a Latinate ending chosen in place of the more familiar "-ian". The word is a near twin of "tellurium", the chemical element, which was named after the same Latin root. Both come from "tellus", so the two words are doublets: different English forms that descend from one source. The element was named in the same period, but the instrument's name was Martin's own invention, which is why a single Latin stem ended up labelling both a machine and a metal.