A Superb Early Victorian antique rosewood improved air 'Sympiesometer'.c.1840. Made by Alexander Adie of Edinburgh(1775-1858) and retailed by Ross of Sunderland (w.1830-50) and numbered 2517. Silvered engraved scale with thermometer and pressure reading scale with vernier marker slide. Bevelled edge glass to the stepped pediment case. Very rare. Full working order. Superb quality and condition. Measures 3.5" x 24.5"long x 2"deep. Stock no.33614. * Alexander James Adie FRSE MWS (1775, Edinburgh – 4 December 1858, Edinburgh) was a Scottish maker of medical instruments, optician and meteorolog...ist. He was the inventor of the sympiesometer, patented in 1818. Adie's sympiesometer is a glass tube filled with coloured almond oil with a gas bulb filled with hydrogen at the top. A thermometer registers the temperature and the sliding brass scale of pressures slides against a fixed scale of temperatures. Alexander Adie patented his design of a special barometer in 1818. It was more portable than a mercury barometer and could be used at sea or for measuring the height of mountains: air pressure decreases by height at a known constant. Captain Fitzroy took one on his famous Beagle voyage.