A FINE VICTORIAN LACQUERED BRASS FORTIN-TYPE LABORATORY MERCURY STICK BAROMETER Negretti and Zambra, London, late 19th century The instrument with slender square section case pierced with a vertical slot to reveal the tube incorporating sliding silvered Vernier slide reading against silvered scale calibrated in barometric inches to the right and millibars to the left beneath serial number 1838 to upper margin, the shaft with Vernier adjustment disc to right over signature NEGRETTI & ZAMBRA, Scientific Instrument Makers to Her Majesty, LONDON to throat and applied mercury tube thermometer with large bulb within brass protective housing and Fahrenheit scale inscribed directly onto the tube, the base with square glass chamber enclosing mercury and incorporating inverted ivory level pointer to interior clamped between horizontal plates over cylindrical chamber and adjustment screw to base, mounted via a brass ring to top and base collar-bracket with triple securing screws onto a rectangular moulded oak panel applied with an ivorine plate further inscribed NEGRETTI & ZAMBRA, Scientific Instrument Makers, to Her Majesty, LONDON fitted into a rectangular cabinet with moulded cornice over rectangular bevel-glazed door. The instrument 104cm (45ins) high; the cabinet 140cm (55ins) high, 26cm (10.25ins) wide, 19cm (7.5ins) deep. 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 is in good condition with only minor discolouration/mellowing and the Vernier slide is operational. The brass case is in good condition although has probably been polished at some point (original lacquer removed) and the finish is generally a little dull/oxidised. The cabinet no longer has its original clasp for the door (has been substituted for a pivoted hook clasp) and has some noticeable bumps and scuffs to the exterior otherwise is in sound original condition. Condition Report Disclaimer