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external coil spring
brass, glass, nickel silver, silvered brass, steel, wood
This barometer is part of the private collection of our friend and fellow collector Michael Böttcher (Germany). All photographs were kindly provided by him.
Before us is a rare and structurally unusual French Atmos-barometer, dating to approximately 1875 and most likely produced by Jules Richard. The instrument is housed in a compact rectangular mahogany case with deliberately austere proportions. The case is fitted with a glazed front panel, allowing direct observation of both the scales and the mechanism itself, a feature that aligns the instrument with laboratory and demonstrational devices of the second half of the 19th century. A metal carrying handle mounted on the top of the case indicates the semi-portable nature of the barometer and its possible use outside a fixed interior setting.
On the left is a vertical registration plate bearing the barometric scale, executed in silvered brass. The scale is graduated in centimetres of mercury and spans a range of approximately 73 to 79 cm, corresponding to the continental metric system adopted in France and Central Europe during the second half of the 19th century. The scale is supplemented with standard textual weather indications in the German language (Sturm, Regen, Veränderlich, Schön, Trocken, etc.), indicating that this particular example was intended for the German-speaking market, or more broadly for Central Europe.
On the right-hand side of the case is a second, horizontal silvered plate engraved “Atmos-Barometer,” carrying two miniature curved thermometers. On the left is a mercury thermometer graduated in degrees Celsius; on the right, a spirit thermometer graduated in degrees Réaumur, distinguished by its characteristic reddish coloration. The plate also bears the French patent designation Breveté S.G.D.G., indicating the French origin of the mechanism and its status as an export product.
The internal mechanism represents one of the most original aneroid constructions of its time. It is mounted on a substantial brass base plate and supported by turned brass pillars. At the heart of the system are two horizontally arranged aneroid capsules, working in tandem to enhance both sensitivity and stability of the readings.
The movement of the capsule membranes is transmitted to an L-shaped main lever mounted on knife-edge pivots, a solution that significantly reduces friction—an approach more commonly associated with barographs than with conventional aneroid barometers. The force then acts upon a single steel helical spring working in compression, which provides stabilization and mechanical balance. Through a system of short levers and linkages, the impulse is conveyed to the indicator hand, which travels along the vertical barometric scale. Of particular note is the trend-setting pointer, brought out to the front panel, allowing the user to manually set a reference pressure mark.
The Atmos Barometer represents a rare transitional form between the classical aneroid barometer and more complex recording systems. It combines engineering ingenuity, experimental mechanical design, and a strictly functional aesthetic characteristic of the French instrument-making tradition of the second half of the 19th century. This instrument is of interest not only as a measuring device, but also as a material document of the search for optimal aneroid construction, reflecting a period of active development and reassessment of the principles governing atmospheric pressure measurement.
