Dialling hemisphere, perhaps belonging to Henry Cavendish

This mechanical device, known as a dialling hemisphere, enables co-ordinates to be transferred graphically between two frameworks. It has no maker's name on it, but a pencilled manuscript label on the underside of the stand suggests that it may once have belonged to the English natural philosopher, Henry Cavendish (1731-1810). It came from the natural philosophy class at the University of Edinburgh.

This device is on a wooden base, and consists of two fixed metal semicircles which project from the front at 90 degrees to each other. There are two other adjustable semicircles, which move across the fixed ones: these are marked in degrees.

This object can be identified with an item in the 1819 inventory, as a 'dialling sphere (From Jones London) £6.6.[0]'. W. & S. Jones were mathematical and philosophical instrument retailers, who also purchased second-hand instruments for resale.

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