A black japanned Kew pattern marine barometer with Gold slide thermometer Negretti & Zambra, Lond

A black japanned Kew pattern marine barometer with Gold slide thermometer Negretti & Zambra, London, circa 1940. With brass cap above glazed cylindrical silvered vernier scale calibrated in millibars signed NEGRETTI & ZAMBRA, LONDON and inscribed BAROMETER, MARINE MK.2. REF. MET. 1542, the cylindrical shaft with brass vernier adjustment knob, gimbal wall mountings, STANDARD CONDITIONS plate and mercury thermometer with Gold type adjustable scale above cylindrical steel cistern cover, 91cm high, in original pine carrying case, 100cm high overall, B.C. Ref. 93. Illustrated in Banfield, Edwin BAROMETERS Stick or Cistern Tube page 179 and described on page 178. The firm of Negretti & Zambra is recorded by Banfield as being established when a partnership between Enrico Negretti and Joseph Warren Zambra was formed in 1850. The firm expanded rapidly throughout the 19th century to become one of the largest manufacturers of scientific instruments and continued trading throughout the 20th century. In 1914 E. Gold of the Meteorological Office suggested adopting the millibar as the unit to be used for measuring atmospheric pressure and it was consequently adopted for daily weather reports from 1st April 1914 and was used on Station and Marine barometers from this date onwards. On the current example the thermometer incorporates a series of slides to the scale which were also devised in 1914 by E. Gold and allow corrections to be made for latitude, height of cistern above mean sea level, mean Index error as well as temperature for any given barometer reading. The barometer also incorporates a capillary bore contraction and Bunten air trap to the tube to assist in its use at sea. The silvered scale is numbered MO.M4694/44/54/58 which indicates that the instrument was returned to the makers for checking in 1944, 54 & 58, the Gold thermometer scale has a similar series of check date numbers. This barometer is an example of the final fully developed mercury marine barometer and retains its original pine packing case.