A rare Regency mercury balloonist's stick barometer Cox, London, early 19th century With brass suspension ring above hinged long rectangular door enclosing canted silvered Vernier register plates calibrated from 20 to 31 inches divided into tenths and annotated with the usual observations to the upper left section over signature Cox, London, and signed John Augustus, the inside of the door now applied with mercury Centigrade and Fahrenheit scale thermometer, the rectangular section trunk with slightly bowed sides above stepped moulded ebonised cylindrical cistern cover, 91.5cm (36ins) high; with a brass wall mounted suspension hook. The current lot was almost certainly made by James Cox who is recorded in Clifton, Gloria Directory of British Scientific Instrument Makers 1550-1851 as an optician, mathematical and philosophical instrument maker working in the Parish of St. Giles, Cripplegate, London from 1810. He is subsequently noted as working from 3 Beach Street, Barbican from 1816 and several addresses including 5 Barbican, 51 Banner Street (St. Lukes) and 85 Lombard Street from 1822 until 1855. A related instrument (also by Cox) was sold at Bonhams, London Fine Clocks 17th June 2008 (lot 13) for £3,600. The scale ranging down to 20 inches would allow the balloonist to take readings up to just over 10,000 feet in altitude.