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A116-24 · Aneroid
c.1870
Object Overview
Before us is a Brass-cased Dutch aneroid barometer, manufactured approximately around 1870 by the French company PHBN for the Dutch firm A. Reballio & Zoon. The instrument represents a characteristic example of an early Continental aneroid barometer of the second half of the nineteenth century, combining a French-made mechanism with an appearance specifically adapted for the Dutch market. The dial directly bears the retailer’s name, A. Reballio & Zoon, Rotterdam, while the PHBN mark on the rear cover indicates the French origin of the barometric mechanism and case.
aneroid capsule tensioned on a C-spring
brass, glass, mercury, nickel silver, silvered brass, steel, wood
The barometer has survived together with an elegant ebonized wooden stand, transforming what was originally a hanging instrument into an expressive tabletop object. The stand is executed in an architectural manner characteristic of decorative objects of the middle and second half of the nineteenth century: a substantial stepped base supports a broad curved cradle in which the circular barometer case is held by four decorative round stops. This arrangement is not part of the measuring mechanism itself and most likely served as a purpose-made tabletop holder, allowing the instrument to be displayed in an interior.
The barometer itself is housed in a barrel-shaped brass case with a smoothly profiled side wall. At the top of the case is a small suspension ring, confirming that the instrument could also be used in the traditional hanging position. The front of the case is closed by a relatively thin brass bezel fitted over the main body. This bezel retains a flat mineral glass with a bevelled edge, through which both the dial and a substantial part of the mechanism are fully visible.
At the centre of the glass is an independent brass trend pointer, fitted with a knurled turning knob. It is not connected to the barometric mechanism and is set manually opposite the current position of the main pointer, allowing the direction of subsequent pressure change — rising or falling — to be assessed. Such a device was extremely common on domestic aneroid barometers of the nineteenth century and enabled the user to judge the barometric tendency quickly without having to remember the previous reading.
The dial is of an attractive open type and is made of silvered brass. Its central section is cut away, allowing the barometer mechanism to remain visible from the front and become an integral part of the decorative composition of the instrument. This type of arrangement is particularly associated with more elaborate models, in which the technical construction was deliberately exposed rather than concealed.
In the upper part of the dial, the barometric scale is arranged in an arc and calibrated in centimetres of mercury over a range of approximately 72 to 80 cm Hg. The divisions are finely executed, consistent with the instrument’s function as a genuine measuring barometer rather than merely a decorative weather indicator.
Along the outer edge of the barometric scale is an extensive weather indication in Dutch. The inscriptions read:
STORM — W. Regen — R. Wind — VERANDERLIJK — Mooi W. — Bestendig — ZEER DROOG
The scale thus associates particular pressure ranges with conditions such as storm, rainy weather, wind, changeable weather, fine weather, settled weather, and very dry weather. Such verbal weather scales should be understood as traditional empirical interpretations of atmospheric pressure, widely used on domestic barometers during the nineteenth century.
In the lower part of the dial, a separate centigrade thermometer scale is arranged as a semicircular arc, covering approximately –10 to +50 °C. Below it appears the inscription CENTIGRADE THERMOMETER. The scale serves a built-in mercury thermometer of unusual curved form.
The thermometer itself is mounted directly on the face of the instrument. Its glass capillary follows the curve of the lower part of the dial, while the spherical mercury bulb is positioned on the left and is not recessed into the case, as was often done on later combined instruments, but is instead openly mounted directly on the dial. This arrangement is both functional and decorative, giving the thermometer equal visual importance within the overall composition.
The central opening reveals the construction of the barometric mechanism. Its sensitive element is a corrugated aneroid capsule made of nickel silver. The hermetically sealed and partially evacuated capsule deforms in response to changes in external atmospheric pressure: it contracts as pressure rises and expands as pressure falls.
The upper wall of the capsule is connected to a substantial C-shaped steel spring, which serves as both a force-bearing and transmission element within the system. The lower end of this spring is secured to a heavy cast-iron crosspiece, itself supported on brass pillars. This construction creates a rigid base against which the extremely small movements of the aneroid capsule are transmitted.
From the upper part of the spring extends a slender and finely made main lever, which amplifies the vertical movement of the sensitive element. By means of a small connecting rod, it is linked to a rotating angle lever mounted on a pivoted joint. This multi-stage lever system acts as a mechanical amplifier: the minute deformation of the capsule is converted into a considerably greater angular displacement in the pointer mechanism.
The angle lever is fitted with a characteristic spherical brass counterweight, intended to balance the moving system and reduce the influence of the weight of its components on the sensitivity of the mechanism.
From the vertical arm of the angle lever, a fine fusee chain runs to the pointer arbor. It converts the motion of the lever into rotation of the axis carrying the main barometric pointer. The chain transmission provides a very light mechanical connection with minimal backlash and allows small movements to be transmitted without the use of heavier geared transmission directly within the sensitive part of the mechanism.
The external barometer pointer is therefore the final element in a relatively complex mechanical sequence: a change in atmospheric pressure deforms the aneroid capsule, its movement acts upon the C-shaped spring, is then transmitted through the main lever and angle lever to the chain, and finally rotates the pointer arbor.
Overall, this instrument is a particularly expressive example of a Dutch commercial aneroid barometer of French manufacture from around 1870. Additional distinction is provided by the surviving ebonized stand, which transforms a technical measuring instrument into an object of interior culture characteristic of the second half of the nineteenth century. The result is not merely a domestic barometer, but a well-preserved example of the international trade in scientific and meteorological instruments, in which a French manufacturer supplied the mechanism and case while a well-known Dutch firm offered the finished instrument to its local clientele under its own name.