Barometers Realm

This Nickel Plated Brass Pocket Barometer, dating to around 1880 and produced by the optical firm Doninelli, represents a unique example of the era when a gentleman, setting out on a journey, would place a watch in one pocket and a barometer in the other.

The case, made of nickel-plated brass, consists of three parts: a fluted back cover, the central body with a suspension ring, and a fluted rotating bezel fitted with a convex mineral glass and an altitude scale in meters up to 2400 m.

Both the altitude scale and the open dial are made of silvered brass. The concentric barometric scale is calibrated in centimeters of mercury, ranging from 56 to 79. The scale is further complemented by three engraved weather indications (Pluie, Variable, Beau) on the inner portion of the dial.

The open dial reveals the elegant movement of the barometer, featuring a 16-centimeter aneroid capsule made of nickel silver (likely with an internal spring) and a finely shaped balance lever of nickel-plated brass with a counterweight. The main lever of the balance freely descends onto the main shaft, which connects to the pointer arbor through a chain linkage. The motion of the capsule’s upper wall is initially transferred to a blued-steel screw positioned at the center of the balance counterweight. This screw allows adjustment of the amplitude of the lever’s oscillation. A distinctive feature of this movement is that the main pivot shaft of the transmission is not mounted on the principal brass frame (where all other elements are placed), but instead fixed to a small iron plate extending beneath the aneroid capsule. This plate is acted upon by the adjustment screw, whose opening is located on the back of the barometer. This exceptionally interesting mechanism appears to be the work of the French master .