Barometers Realm

Before us is an elegant Mahogany Bulb Cistern Barometer, manufactured by G. Bogia & Co. in Leiden and datable to approximately 1800–1830. This instrument represents the work of a family of Italian émigrés who settled in the Netherlands—hereditary glassblowers whose craftsmanship enabled the production of fine and technically accomplished siphon tubes for mercury barometers. A characteristic feature of such tubes is the small spherical enlargement at the lower bend of the siphon, serving as a mercury reservoir—a detail that is at once functional and visually expressive, reflecting the continuity of the Italian glassmaking tradition.

The case is constructed from pine veneered in mahogany arranged in a distinctive herringbone pattern, while the perimeter is enriched with fruitwood stringing, creating a subtle decorative contrast. The upper section is formed as a broken pediment, surmounted by a brass finial in the shape of an urn—here still retaining its classical urn form rather than assuming the more typical vase-like appearance. Beneath the pediment is a glazed door mounted on brass hinges and fitted with a hook to secure it in the closed position. At the lower end of the case is a circular cover made of solid mahogany, enclosing and protecting the mercury cistern.

Behind the door is the register plate, executed in silvered brass; the quality of the silvering is notably high, and all scales and inscriptions are finely hand-engraved with considerable skill. The barometric scale is calibrated in London inches of mercury over a range from 27 to 31, and is fitted with a sliding vernier allowing readings to be taken to hundredths of an inch. The scale is further enriched with detailed English weather indications, suggesting that the instrument was intended for the English market.

To the left of the barometric tube is a spirit thermometer, the scale of which is graduated in degrees Fahrenheit and provided with a finely engraved system of textual heat indication. The glass capillary terminates in a spherical bulb containing alcohol tinted with a violet dye, enhancing the legibility of the readings.

The barometric tube measures approximately 82 cm in height, with an external diameter of about 10 mm and an internal bore of approximately 4 mm. It is formed as a siphon, the lower return expanding into a small bottle-shaped reservoir. This reservoir is fitted with a cork stopper incorporating a metal pin, allowing the internal channel of the tube to be sealed during transport—a practical solution that enables the instrument to be handled and moved safely.

Taken as a whole, this barometer is a compelling example of the early nineteenth century, combining technical precision, high-quality materials, and restrained architectural elegance, while the construction of its glass elements clearly reflects the legacy of the Italian school, adapted to the conditions of the Northern European market.