Barometers Realm

At the front, the case is covered by a lacquered brass bezel with a fine beaded ornament running along its inner edge. The bezel bears a characteristic stable patina, ranging from deep blue to brown and unevenly distributed across its front surface. It retains a flat mineral glass carrying a brass set hand (trend indicator), operated by a knurled knob at the centre of the glass.

Floating Movement

The heart of the barometer — its movement — sits in a zinc cup that is not fixed to the case, as in conventional aneroids, but rests freely on five cylindrical helical compression springs mounted on the back plate, which press it towards the bezel. The cup is centred by three guide pins rising from the back plate; three of the five springs are threaded onto these pins, while the remaining two stand free at equal spacing.

The springs take up axial play and isolate the movement from deformations of the wooden case. As humidity changes, wood alters its dimensions across the grain by whole percentage points — the case "breathes"; moreover, turned wooden cases inevitably vary in their dimensions. Had the thin-walled zinc cup been rigidly screwed to the wood at several points, seasonal deformations of the case would have been transmitted to the movement base: it would distort slightly, the capsule support would shift relative to the levers, and the result would be zero drift and increased hysteresis — an aneroid being sensitive to displacements of mere microns. On its springs, the movement simply "floats".

The bezel serves as the datum, lightly pressing down the entire stack beneath it. The chain runs as follows: bezel → glass → reflector ring → dial → broad movement bridge → zinc cup → springs → back plate. This is precisely why the bezel is secured here at six points rather than the customary four.

The springs take up axial play without shims or fitting during assembly and, importantly, continue to do so for decades. Screws in wood would have loosened or stripped their holes over 160 years, whereas the preloaded springs still hold everything tight. Despite the passage of a century and a half and the total yet stable corrosion of the zinc cup and back plate, the system looks remarkably neat and effective, as if made yesterday. Besides compensating for play, it also provides incidental shock absorption: an axial knock — for instance, when the instrument is carelessly hung on a wall or transported — is partly damped. But this is a bonus rather than the purpose: preloaded by the bezel, the system works as an elastic clamp, not as a suspension.

Dial

The dial is made of card firmly glued to a zinc disc and is fitted with a separate brass reflector ring. Ordinarily the dial was clamped directly into the reflector ring and set on small seats within the case; here there are no such seats — the floating mounting requires the bezel to hold all the layers in sequence, each upper layer bearing on the next.

In the upper part of the dial, the barometric scale runs in an arc, graduated in Paris inches of mercury and accompanied by the corresponding calligraphic legend "Pariser Zoll". The scale extends from 26 to 30 inches, each inch divided into 24 parts — that is, into half Paris lines (the inch being divided into 12 lines). Along its outer edge the scale carries a detailed seven-term set of verbal weather indications, set in antiqua capitals and separated by full stops: STURM. (storm) — VIEL REGEN. (much rain) — REGEN. (rain) — VERÄNDERLICH. (changeable) — SCHÖN. (fair) — SEHR SCHÖN. (very fair) — BESTÄNDIG. (settled).

At the centre of the dial, the name of the instrument type, "Aneroid Barometer", runs in an arc, rendered in a decorative Fraktur close to Kanzleifraktur (chancery Fraktur), with calligraphic flourishes on the capitals. Below it, set horizontally, is the retailer's signature "H. Lehmann, Berlin." in a condensed grotesque.

In the lower part of the dial, a small straight mercury thermometer with a spherical bulb is mounted horizontally. Its scale is printed on a separate piece of card enclosed in a cartouche frame with a shaped lower edge, and is calibrated in degrees Réaumur from −20 to +40, as indicated by the calligraphic inscription "Réaumur".

Movement

The movement follows the early system of Lucien Vidie, the inventor of the aneroid barometer. By the 1860s his French and English patents had already expired (in the spring of 1858) and the principle had passed into the public domain; in Hamburg, moreover, no patent law of its own existed at all until the introduction of the all-German Patent Act of 1877. This gave R. Deutschbein complete freedom to experiment with the aneroid movement.

At the core of the movement is an evacuated capsule of copper or tombac with deep corrugations, rigidly fixed by its lower wall to a cast-iron mounting plate. The upper wall of the capsule is drawn, via a brass fork with a steel pin, onto a massive brass lever lacquered black on its upper face — a rather unusual choice, since this lever was as a rule made of cast iron. The lever is mounted on two knife-edge bearings and rocks in a vertical plane about a fixed axis.

The long arm of the lever bears on a massive steel helical spring set in a brass cup, which counterbalances the weight of the atmosphere. The stiffness of this spring determines how far the whole two-armed lever tilts per unit of pressure; it also holds the aneroid capsule open, preventing its upper and lower walls from collapsing together. As a result, the slight movement of the diaphragm at the short arm becomes a noticeable swing at the end of the long one: the lever acts as the first multiplier of the movement, amplifying the signal from the few microns by which the upper wall of the capsule deflects under atmospheric pressure to tenths of a millimetre of travel at the end of the long arm.

A small rod fixed at the end of the long arm is connected by a link to a pivoting assembly, where a bell crank with unequal arms turns on pivots set between centres. Its vertical arm transmits the motion to the pointer arbor by means of a fusee chain. The supports of the bell crank are made of brass and carried outside the cast-iron mounting plate, and — notably — are angled downwards at approximately 45 degrees. The pointer arbor carries the indicating hand, likewise lacquered black, with a crescent-shaped counterpoise; tension on the fusee chain is provided by a conventional hairspring on the pointer arbor.

The movement is in impeccable condition.

Conclusion

The scale in Paris inches and the Réaumur thermometer place the instrument before the German lands adopted the metric system, which became compulsory in 1872, and accord well with a date of 1860–1870 — a period when German makers, having mastered Vidie's principle, were seeking design solutions of their own. Deutschbein's barometer is a vivid testimony to that search. Its movement combines Vidie's classic layout with details unusual for it — a brass main lever and the outboard, angled supports of the bell crank — while the floating, spring-loaded mounting reveals a profound understanding that an aneroid's accuracy depends not only on the capsule and the transmission, but also on how the movement relates to its case. The solution, which isolates a sensitive movement from "breathing" wood and compensates for play on its own, proved so successful that a century and a half later the instrument remains tightly and precisely assembled. It never gained wide currency: for a mass-produced domestic barometer it was more complex and costly than ordinary screw fixing, and once the industry moved back to predominantly metal cases, it lost its former urgency. All the more valuable, then, is this example — a rare specimen of engineering thought from the early period of German aneroid production, preserved complete in its original form and in excellent condition.