Barometers Realm

This Black Forest Carved Walnut Aneroid, circa 1860, signed by the Hamburg optician D. Köhn, is housed in a walnut wood case with deeply sculpted relief carving. Walnut is not accidental here: its grain is dense and resilient enough to support complex three-dimensional carving, yet it possesses a warm, soft tone that, when polished, reveals depth and a velvety luster. The natural play of light across the carved surfaces is especially striking—when in shadow the case appears dark and saturated, but when turned toward the light, amber and honey undertones emerge.

Compositionally, the case is designed as a wreath of interlaced oak leaves arranged in a circular form. This is a characteristic aesthetic motif of German-speaking regions (especially the Harz and the Black Forest), where barometers were often adorned with natural forest imagery—the forest symbolizing endurance, seasonal renewal, and the natural flow of time. Here the leaves are not merely engraved in flat silhouette, but carved plastically, with modeled veins, folds, and softened transitions, giving the ensemble a sculptural sense of mass and depth.

The barometer, set within its walnut frame, appears to be “nested” in a natural environment, as though the mechanism and the wood form a single organism.

Unfortunately, the original large upper portion of the case was removed by a previous owner; the entire top element once housing the thermometer and its surrounding carving is missing. Most likely the opaline glass scale plate of the thermometer was broken—a common type of damage for these barometers—and the owner chose to cut away the upper section entirely.

The exposed dial is made of card, and the barometric scale is calibrated in Paris inches of mercury, typical of early aneroid barometers. Each inch is divided into 24 subdivisions. The scale includes the standard German weather indications. The pointer is made of blued steel, shaped elegantly with a crescent-form tail. The dial is protected by a thick mineral glass with a faceted edge, set into a brass bezel with a reflective inner ring. At the center of the glass is a settable trend marker with a knurled adjustment knob.

However, the most remarkable feature of this instrument is its early movement of exceptional beauty. The large aneroid capsule is of an unusual form: instead of the familiar multi-corrugated membrane, it has a smooth, almost disc-like diaphragm with only a few shallow reinforcing ribs. The capsule is made of pure or lightly alloyed copper, rather than nickel silver. Another striking detail is that after the two diaphragm halves were soldered together, the outer perimeter was painted black.

The capsule is braced by an external coil spring, held against a substantial cast-iron lever, which rests on two finely pointed rods. Instead of a fusee chain to transmit motion to the indicator arbor, a thread linkage is used. An additional notable feature is that the entire movement is mounted at a deliberate angle within the case—presumably for visual emphasis and aesthetic effect.

This barometer is a rare early example of a mid-19th-century aneroid, combining an exposed copper capsule with an elegant carved walnut case, making it not only a precise instrument but also a refined decorative object of its era.