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Object Overview
Before us is a French aneroid desk barometer, made around 1890–1900 and intended both for use on a table and for hanging. The instrument is a particularly interesting example of the Franco-Belgian trade in meteorological instruments at the end of the nineteenth century, since its dial bears two distinct trade markings. On either side of the scale are the inscriptions FREMY — BRUXELLES, while at the bottom of the dial appears the SL mark with a three-branched candelabrum — the characteristic emblem of the Société des Lunetiers.
The most probable attribution of this barometer therefore involves not one but several participants in the commercial and manufacturing chain. Fremy, for whom no reliable biographical or commercial information has so far been found, was apparently a Brussels retailer. The Société des Lunetiers most likely acted in this case as a French wholesaler or distributor. Finally, the barometric movement itself may have been manufactured by one of the specialist French factories that supplied such mechanisms to instrument dealers and optical firms. Possible makers include, for example, .
n/a
rack and pinion
brass, cardboard, glass, nickel silver, nickel-plated brass, steel
The instrument is housed in an elegant circular case, only 95 mm in diameter, with a characteristic barrel-shaped profile. Its sides are formed by several gently projecting concentric mouldings, giving the case considerable depth and making it resemble a miniature drum or barrel. The case is made of brass, and its surface is carefully polished, further emphasizing the characteristic colour of the material.
At the top is a bow fitted with a movable suspension ring, allowing the barometer to be hung on a wall. The ring itself does not appear to be original and was probably replaced at a later date. It is apparently made of bronze and differs in colour from the warmer brass of the case; this contrast is particularly evident where the two metals meet.
At the bottom are two small feet of nickel-plated brass. Together with the projecting lower part of the case, they allow the barometer to stand securely on a horizontal surface. The instrument was therefore originally conceived as a versatile piece: it could either be suspended from its upper ring or placed on a table, desk or mantelpiece.
The front of the case is closed by a separate metal bezel, tightly fitted over the main body and at the same time retaining the protective glass. It is currently fitted with a convex mineral-glass crystal, but this is almost certainly a later replacement. The clearest indication of this is the absence of the second, manually adjustable trend indicator hand normally found on aneroids of this type. Such a hand was mounted at the centre of the glass and set by turning a knurled knob, allowing the current position of the barometric pointer to be compared with an earlier reading. In all probability, the barometer originally had a flat mineral-glass crystal, which was subsequently broken or lost. During a later repair it was replaced with an ordinary convex watch crystal of a suitable diameter.
The barometer is fitted with an open dial, through the central opening of which the aneroid movement can be observed. This arrangement transforms the mechanism from a purely functional component into an integral part of the decorative design of the instrument.
The dial itself is made of cardboard and takes the form of a broad white ring with a thin brass rim around its central opening. It carries a concentric barometric scale graduated in centimetres of mercury from 69 to 80 cmHg. Each centimetre is divided into twenty smaller divisions, allowing the pressure to be read to half a millimetre of mercury.
Outside the scale is the traditional textual weather indication in French, ranging from stormy and rainy weather at low atmospheric pressure to very dry weather at high pressure. The inscriptions are printed in capital letters using a distinctive combination of serif and sans-serif typefaces, with certain particularly important terms emphasized in larger lettering. This typographical composition gives the dial the characteristic appearance of French instruments of the period.
The principal indicating hand is made of extremely thin blued steel. Its long working end terminates in a small arrow-shaped point, while the opposite end forms an elegant crescent-shaped counterweight. The dark blue surface of the blued steel contrasts effectively with the white dial and the golden components of the movement.
At the heart of the barometer is a large circular corrugated evacuated capsule made of nickel silver. It occupies almost the entire area beneath the movement and is clearly visible through the open centre of the dial.
Unlike designs employing an external loading spring, here the opposing elastic force is provided in part by a helical spring located inside the aneroid capsule. As atmospheric pressure rises, the membranes of the capsule move closer together; as the pressure falls, the capsule expands. These microscopic changes in its thickness must be considerably amplified before they can be transmitted to the indicating hand.
A tiny push-rod is positioned on the upper membrane of the capsule. As the capsule expands or contracts, this transmits its movement to a rocking arbor mounted beneath the shaped brass movement plate. The arbor itself is carried on pivots in bearing holes and is capable of a small angular movement.
From this arbor, a second push-rod rises through an opening in the shaped plate and transmits the movement to a toothed sector. In this way, the extremely small vertical displacement of the capsule membrane is converted first into a rocking motion and then into a substantially amplified angular movement.
The toothed sector engages with a small pinion on the central hand arbor. A fine spiral return spring — the hairspring — is fitted to the same arbor. It continuously takes up backlash in the gearing, keeps the teeth engaged against one side, and ensures a steady and smooth movement of the hand as atmospheric pressure changes.
The entire transmission mechanism is mounted on a decoratively shaped brass movement plate. Its symmetrical cut-outs and profiled edges serve not only a structural but also an aesthetic purpose: because the movement was deliberately left exposed to view through the dial, its components were finished with considerably greater care than would have been necessary in a completely enclosed barometer.
This barometer is a characteristic yet particularly attractive example of a French open-dial aneroid of the late nineteenth century, in which the technical construction was deliberately made part of the visual design. The golden barrel-shaped case, white annular dial, slender blue hand and exposed shaped movement create a striking contrast, while the possibility of either hanging the instrument or standing it on its own feet makes it an unusually versatile domestic barometer.
The inscriptions Fremy Bruxelles and the small emblem of the Société des Lunetiers provide a glimpse into a commercial system that is usually concealed behind a single name on the dial. As a result, the barometer is of interest on several levels: as a meteorological instrument, as an example of decorative French instrument-making, and as material evidence of the complex manufacturer — wholesaler — local retailer network through which French scientific and domestic instruments reached the Belgian market at the end of the nineteenth century.