A LATE VICTORIAN LACQUERED BRASS FORTIN-TYPE LABORATORY MERCURY STICK BAROMETER Negretti and Zambra, London, late 19th century The instrument with slender cylindrical case pierced with a vertical slot to reveal the tube incorporating sliding Vernier collar reading against a silvered scale calibrated in barometric inches bordering the right hand side opposing millibar scale to the left, the shaft with Vernier adjustment disc to right over engraved signature H. Negretti & Zambra, 1 Hatton Garden, 122 Regent St. W. & 39 Cornhill, London and applied mercury tube FAHRENHEIT thermometer with canted silvered scale and enclosed bulb to front, the base with cylindrical glass chamber enclosing mercury and incorporating inverted ivory level pointer to interior clamped between horizontal plates over cylindrical cistern and adjustment screw to base, mounted via a brass ring to top and base collar-bracket with triple securing screws onto a rectangular ogee moulded walnut panel with curved top and base and inset with a brass-bordered trade plate inscribed NEGRETTI & ZAMBRA. METEOROLOGICAL, INST'T MAKERS, TO HER MAJESTY, 1 HATTON GARDEN E.C., 59 CORNHILL E.C., 122 REGENT ST. W., LONDON. to centre. The instrument 102cm (40ins) high; the wall panel 103cm (44ins) high, 14cm (5.5ins) wide. Provenance: The Selwyn Demmy Collection. The firm of Negretti & Zambra are recorded in Banfield, Edwin BAROMETER MAKERS AND RETAILERS 1660-1900 as being established in 1850 when a partnership between Enrico Negretti and Joseph Warren Zambra was formed. The firm became one of the most prolific makers of scientific instruments and continued trading well into the 20th century. The current lot is made to the principles laid down by Nicholas Fortin (1750-1831) and incorporates a glazed cistern so that the level can be calibrated via the adjustment screw to the base against an inverted conical ivory cone in the cistern in order to obtain consistency in the readings. This particular type of barometer provides an accurate reading hence was generally adopted for laboratory use throughout the 19th and early 20th centuries. Condition Report: Instrument is filled with mercury and provides a good reading with no apparent airlocks. The silvering to the scales has discolouration/mellowing, the Vernier slide is operational. The brass case is in sound condition but has patchy strong discolouration and wear to the original lacquered finishes. The back panel has some historic age related bumps, scuffs shrinkage and discolouration/blooming to the finish. Condition Report Disclaimer