Mural Quadrant, by John Bird, London, c. 1767

A 32-inch quadrant with a telescopic sight - an instrument to be mounted on a wall and used for measuring the positions of stars. Thomas Hornsby became Savilian Professor of Astronomy in 1763 and was the chief instigator of the Radcliffe Observatory, founded in 1772. There he was able to install much larger measuring instruments, also made by Bird, two of which are displayed on the Museum staircase, including an 8-ft mural quadrant. Before the foundation of the Observatory, Hornsby had used the smaller quadrant to determine the latitude of Oxford as 51 degrees, 45 minutes, 15 seconds.