The barometer stands approximately one metre high and has its original lacquered and black finish. It is virtually identical to that made by Short and Mason, London (cat no.109), also shown in the picture. There is a plate attached to the front marked in inches from 6 to 31. A small metal mark with a stopper screw is attached to the front of the barometer. The bottle and the mercury are no longer attached. The glass tube that contains the mercury sits behind the plate in a metal housing. The tube extends below the surface of the mercury into a cistern of much larger cross section than the tube (it was not possible to make the cistern barometer portable until they could make the mercury tube sufficiently small ), so that the rise and fall of mercury is small but not negligible in comparison to that in the tube. To compensate for the change in the mercury level the scale graduations have been foreshortened.. In meteorology mercury barometers are used to measure the atmospheric pressure.
MW