Armillary Sphere

A skeleton sphere suggested by concentric rings which represent the relative positions of the celestial circles of the equator and the ecliptic revolving within a horizon and meridian divided into degrees of longitude and latitude. It was invented by Eratosthenes (q.v.), who by this means computed the size of the Earth, and inclination of the ecliptic to the equator; also the latitude of the city of Alexandria. The armillary sphere is frequently used as a decoration, such as the beautiful specimen cast in bronze and supported on the shoulders of Atlas, which adorns the entrance to Rockerfeller Plaza in New York.

DeVore, Nicholas. Encyclopedia of Astrology. New York: Philosophical Library, 1947.