AN UNUAL MERCURY TUBE DEMONSTRATION STICK BAROMETER IN BOW-FRONTED GLAZED MAHOGANY CASECHADBURN, LIVERPOOL, CIRCA 1860With fully exposed tube spended from an ornamental scroll-shaped lacquered brass bracket at the top with the base immersed in a simple cylindrical glass cistern with circular cap resting on a brass collar and supported from underneath by a disc applied to conforming bracket, the upper section with genero silvered twin Vernier scales calibrated in barometric inches and labelled Registered 8am and Registered 8pm respectively beneath signature CHADBURN, OPTICIAN &, Instrument Maker, To HRH Prince Albert, Lord St. Liverpool, to upper margin, contained in a mahogany D-shaped case with stepped inverted ogee moulded top over full height half-round glazed front door and conforming moulded base.107cm high (42ins) high, 22cm (8.5ins) wide, 18.5cm (7.25ins) deep.Provenance: The Selwyn Demmy collection.Chadburn Brothers are recorded in Banfield, Edwin, BAROMETER MAKERS AND RETAILERS 1660-1900 as 'notable makers' working from Albion Works, 26 Nursery Road, Sheffield and 71 Lord Street, Liverpool circa 1837-75.The current lot appears to have been designed to allow the working principles of a barometer to be clearly seen and presented in a high-quality manner. From this it would be reasonable to suggest that the instrument was perhaps made for showroom e, a thought that is backed-up by the full signature to the plates, or for a wealthy gentleman's home laboratory. The present barometer can also be fairly accurately dated as the double scales follows Admiral Fitzroy's principles which he first introduced in around 1857, hence the instrument would have been made after that date but before the death of Prince Albert in 1861.