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gravitational
brass, glass, nickel silver, steel
This visually captivating Mysterious Barometer, dating to around 1925 and produced by the renowned German company C.P. Goerz — one of the greatest brands in photographic history — represents a unique instrument whose mechanism is based on the force of gravity.
The barometer’s case is designed as an elegant table stand made of solid brass with a soft golden shade. The form of the base may be described as a “flared bell”: a wide, gently curved foot gradually rises upward, transitioning into a narrow neck that supports the round dial housing. Thanks to this silhouette, the instrument appears simultaneously austere and refined, emphasizing its distinctive “mysterious” character.
The upper part of the instrument consists of a circular brass bezel holding two thick round glass plates with faceted edges, set a short distance apart. This construction is one of the trademark features of Goerz models. The rear glass functions as the dial plate — the barometric scale is printed directly on its inner surface. The front glass serves as protection, yet also carries the trend indicator hand, controlled via a central knurled brass knob. This indicator is used to mark a previous pressure value, allowing the user to track the trend of atmospheric change.
The concentric barometric scale is calibrated in millimetres of mercury, ranging from 720 to 790 mmHg. Of special interest is the textual weather indication placed outside the scale ring. The inscriptions are in Czech, indicating the market for which this particular example was produced. Full translation:
This unusual barometer differs fundamentally from most aneroid instruments. Its key feature is the separation of the measuring mechanism and the indicating mechanism. These two modules are connected by only one component: an extremely thin yet strong phosphor-bronze wire, about 100 mm long. This highly elastic wire transmits only pulling force, never pushing. At the level of the indicating mechanism, the wire is attached by a screwed joint to the fusee chain driving the pointer shaft; at the level of the measuring mechanism, the wire forms a small hook that engages with the pin of the upper lever.
The 46 mm nickel-silver aneroid capsule contains an internal leaf spring. The system of amplifying levers — consisting of a lower and an upper lever — is actuated by the upper membrane of the capsule through a small pusher soldered to the membrane. The pusher contacts the lower lever and transfers the movement of the capsule’s sensitive wall. A long pin extending from the lower lever connects to the upper lever, further transmitting and amplifying this motion upward — to the control wire.
On the lower lever, the membrane’s movement increases in the same direction as the membrane’s motion. On the upper lever, the amplification is somewhat smaller, and the resulting direction is opposite to the membrane’s movement. In the indicating mechanism the direction is reversed once more. Thus, the downward movement of the membrane — corresponding to a rise in atmospheric pressure — ultimately becomes a clockwise rotation of the pointer.
Calibration of the instrument is carried out on the lower plate at the base of the instrument, using an adjustment screw. Turning the screw raises or lowers the entire bridge carrying both levers. The barometric level of the instrument is set directly to sea level, as indicated by the inscription at the bottom of the dial. To determine the pressure corresponding to sea-level conditions when a mercury barometer is available, a height table is placed on the base of the desk barometer, allowing the required setting value to be easily calculated.
This table barometer by C.P. Goerz is a rare example of the harmonious combination of engineering precision, decorative elegance, and an original construction based on a glass dial. It reflects the transitional period of European instrument-making in the 1920s, when scientific devices simultaneously became interior objects, and today remains a valuable collectible.
