Forecasting aneroid barometer of lacquered brass construction, 3⅝” diameter silvered die-struck dial with barometric range from 28 – 31 inches of mercury, divided to 1/10ths of an inch, the upper portion marked “Forecasting Aneroid,” the lower “Compensated,” signed by the maker “Negretti & Zambra, London” with “N&Z” logogram. Fine blued steel pointer set beneath bevelled glass retained in a rotating bezel with index. First quality lacquered brass movement of conventional pattern set on a gilt chassis and driven by a single 2″ capsule. Type one drum form case, the circumference marked with altitude correction scale from sea level to 3,000 feet, altitude index locked to position at crown.
4¾” lacquered brass forecaster of tri-concentric design, having 1st pattern swinging easel type stand. Signed by the maker “Negretti & Zambra,” with patent date 1915. The whole contained within a pigskin over timber green velvet-lined case with separation squab, snap closure and button release.
Of the many instruments Negretti & Zambra produced, two stand out: the Weather Watch and this, its big brother the Forecasting Aneroid, essentially a much more user friendly version of the Weather Watch, made in significantly small numbers as a special order item only. Negretti & Zambra spent around 10 years developing the forecaster, and, if used correctly, can be around 80% accurate.
Altitude correction is achieved by turning the crown anti-clockwise – the entire back of the instrument may then be rotated so that the triangular index may be aligned with the required station altitude. The reading shown on the dial will then translate to a value at sea level at one’s location.
The barometer the subject of a full disassembly and inspection, re-build and calibration under laboratory conditions. The barometer is sensitive and has good transition with demonstrably very acceptable accuracy, see performance graph below.
This Forecasting Aneroid set remains in entirely original condition, save the replacement of the two silk ribbons. The barometer retains virtually all its original finish, the dial bright and vibrant with minor discolouration to bottom. The forecaster retaining the greater proportion of its original finish, the jappaned verso with some losses. The case is sound in all respects, slight damage to top front, the leather with some signs of age, the fabric interior bright and verdant with some losses to side trim.
A very good example in absolutely collectable condition.
Dimensions: 5½” wide x 6″ deep x 2¾” high
Stock No: CP0875
Price: Vavasseur Archive