Bourdon barometer having 4¾” printed open centre glazed card dial, the outer part marked with standard meteorological terms, the lower annotated “Metallic Barometer” with twin medallions for Gold Medal Exhibition 1849, cited as E. Bourdon & Richard’s Patent, Paris,” and Universal Exhibition London 1851, cited as a “Council Award.” The inner barometric scale calibrated in inches of mercury with a range from 28 – 31 divided to 1/20ths”. Finely cut and polished bevelled glass with trademark Bourdon pierced gilt index. Early pattern movement, the beam chassis struck with Bourdon & Richard logogram and serial no. “8138”, and a further no. “152”, possibly a pattern number. All contained within a standard drum form case, bayonet fitting front bezel and back cover, the verso centre with adjustment port. Extension post and suspension ring.
Condition: The subject of a full service and conservation work, tested and checked under laboratory conditions.
The glass chip free but with minor scratch toward centre. The dial clean and crisp, the very bottom with slight peripheral damage. The movement with some ageing but with bright colour and presenting as good. The pointer retaining most original blueing, some small points of oxidation. The case generally with patches of oxidation, retaining much original lacquer. Both front and rear rings with wear and oxidation.
Comments: Bourdon & Richard barometers differ markedly from the common form of aneroid barometers: both essentially operate on the same principle though the execution of the mechanism is quite different. The Bourdon utilises a horseshoe-shaped capsule arranged around the outside of the mechanism – it is roughly a flat oval in section, acting on twin connecting rods driving a very finely constructed fan-shaped rack which, in turn, is engaged to a pinion set at the base of the arbour. These instruments are known for their great accuracy, sensitivity and gentle transition: in short they were the finest aneroid barometers of the 19th century.
The upper back plate stamped with the cartouche “EB,” marking the production of Felix Richard for Eugene Bourdon, and the lower backplate the serial no. “8138,” as well as “Richard a Paris.” The rack with the earlier ‘pointed end’ design. The cartouche, the rack and the serial number indicate a date c1860.
The fascination for the Bourdon system is easily appreciated in the fine making of the movement, especially the rack and associated pinion. Unlike the movements of Vidi-inspired aneroid barometers, the Bourdon barometer has an attractively lazy speed to indication. This does not make it less accurate, and some would suggest that in fact this design is superior to its main rival.
These instruments are always infrequently found and must be considered scarce. This Bourdon barometer, by far better than average, with complete originality and in good working order, is very desirable, and must be considered rare and in easily collectable condition.
Dimensions: 5¼” diameter x 2¼” deep
Stock No: BA1663