Astronomical regulator by John Shelton

Catalogue description — Royal Museums Greenwich

A one-month duration mahogany longcase regulator by John Shelton, London, circa 1769. The movement is of typical Graham/Shelton form with chamfered corners to the tall plates which are united by six latched knopped pillars. The five wheel train is driven by a brass cased cylindrical lead weight suspended on a brass pulley with double line to the going barrel (17 turns). The train wheels all have four curved crossings except for the fine brass escape wheel which has six straight crossings and is triple screwed to a short brass collet. The movement is fitted with vertically pivoted stop work, bolt and shutter maintaining power and Graham type long shank steel pallets fitted with ruby nibs. The backplate is fitted with two screwed end plates, the uppermost plate is inscribed 'The pendulum spring & escapement by John R. Arnold . Anno 1816'. The top of the crutch is fitted with two hand screws for beat adjustment with a pin engaging into a slot within the grid-iron pendulum which runs against a silvered beat scale reading 0-2.5 degrees. The ten and one quarter inch signed silvered regulator dial has an outer minute circle with arabic five-minute marks enclosed by an outer scribe line and inner track, the similarly laid out subsidiary seconds dial has bold observatory marks. The hours are engraved upon a revolving silvered ring mounted to the hour wheel by a push fit frictional collet, visible through an upturned lunette. Both hands are constructed from blued steel; the seconds hand is counterpoised and the finely sculpted minute hand is counterpoised by a semi solid minute wheel and cannon pinion (under the dial). The well figured mahogany veneer is laid onto a mahogany carcass. The case has a flat hood with moulded cornice over rounded corners, moulded sided panels and glazed door. The trunk has a concave throat moulding with moulded rectangular door and stands upon a panelled base with double plinth.