- Armillary Sphere
This armillary sphere is for demonstrating the phenomenon of the seasons of the year and to show either the real motion of the earth or the apparent motions of the heavens. The outer frame consists of two meridian rings marked with degrees of latitude, equatorial and ecliptic circles, and tropic and arctic circles. Inside the Antarctic Circle is another marked out in 24 hours. Inside the outer frame is a rod connecting the poles that carry the globe, a meridian circle marked with the degrees of latitude, and pivoting at right angles, a brass horizon ring. The armillary and the globe are arranged to rotate independently to demonstrate that whichever is at rest, the rising and setting of the sun, is at the same point of the horizon and at the same time. The armillary sphere has its origins in antiquity, and some were used for astronomical measurements. They became essential as an aid to teachers of astronomy.
George Adams, London
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George Adams, London, "Armillary Sphere," in Stevens Digital Collections, Item #272, http://librarycollections.stevens.edu/items/show/272 (accessed April 28, 2017).