A rare mahogany wall mounted mercury barograph, Negretti & Zambra, London, circa 1870

7-inch engraved silvered timepiece dial signed Negretti & Zambra, Inst. Makers to Her Majesty, London, 8-day fusee and chain movement with anchor escapement, the barograph chart drum mounted above and driven by a pinion rising from gearing connected to the rear of the fusee arbor, the pen mounted to the right side with silvered scale calibrated from 28 to 31 inches and controlled by a mercury tube mounted on the backboard, a lever operated by the minute wheel engaging the pen with the drum for fifteen minutes once every hour, a mercury thermometer mounted above, the case with broken architectural pediment above a glazed door with flower carved spandrels on the upper corners, the sides with reeded panels below a moulded cornice, the interior with a spirit level

Admiral Sir Alexander Milne (1806-96) designed a self-recording mercurial barometer in 1857. Within ten years Negretti and Zambra had designed a modified version of the instrument for sale to the general public, and the present lot is an example. For a similar mercury barograph see Edwin Banfield Barometers, Aneroid and Barographs Baros Books 1985 fig.96