Adie & Son - Edinburgh. Mid-19th Century mahogany sympiesometer. 
Good quality and rare, mid-19th Century mahogany-cased Sympiesometer – No. 1978 ; the engraved silvered brass register plates, signed and numbered by the makers and protected by glass cover, bearing original Fahrenheit thermometer and replaced sympiesometer tube, with manually operated calibration slide to the side and circular register dial plate to the base. [24 inches / 61cm] Perhaps the most renowned firm of Scottish Scientific Instrument Makers, Alexander and his son, John [the only instrument makers to be elected to the Edinburgh Royal Society] worked from premises in Princes St. from 1832-57. Adie patented the ‘Sympiesometer’ in 1818, an instrument which, with modifications, was made in significant numbers well into the late 19th Century.