Mural circle

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(Astron.) a graduated circle, in the plane of the meridian, attached permanently to a perpendicular wall; - used for measuring arcs of the meridian. See Circle, n., 3.

See also: Mural

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
President James Madison signed the declaration of war, Royal Astronomer John Pond and other scientists gathered at the Royal Greenwich Observatory near London to watch the summer solstice and collect data using a newly installed 6-foot mural circle. A mural circle is a telescope on a circular frame, mounted on a wall and aligned north/south.
This led to the making of a mural circle for transit observations.