This form of barometer is known as a sympiesometer. The metal face is inscribed with the maker's name: 'PATENT A. Adie Edinburgh N.o 537'. The thermometer scale is marked from 25 to 110 (fahrenheit) with divisions to 0.2F. Thebarometer scale is marked from 27 to 31 (inches of mercury) with 0.02 divisions. Against it runs a sliding scale marked from 120 to 30 with divisions to 0.2. In addition, there is a circular scale at the bottom, also graduated in inches of mercury. The instrument is contained in a wooden glass-fronted case.

The maker, Alexander Adie, developed the sympiesometer in 1818 as a form of barometer especially for use at sea. Instead of having a column of mercury, it used a tube containing oil and hydrogen gas to register changes in pressure. This allowed the size of the instrument to be reduced, making it more convenient for use on ships.