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of 38 Holborn Viaduct, London, EC (1914)
of 5 Leadenhall St, E.C.3. (1921)
Factory: Half Moon Works. Barnsbury, N1 (1921)
of 122 Regent Street, London, W1. Telephone: Regent 3406. Cables: "Negretti, Piccy, London". (1921)
The firm Negretti and Zambra was a photographic studio and producer/factor of optical and scientific instruments, based in London.
See also -
1850 Company founded. Henry Negretti and Joseph Warren Zambra formed a partnership; the firm would eventually be appointed optical instrument makers to Prince Albert, the Royal Observatory and the British Admiralty
The Company later gained patents to improve on the design and construction of its instruments, and in 1851 gained a patent to make thermometers.
1851 The partners were the only English instrument makers to receive a prize medal for meteorological instruments at the 1851 Great Exhibition. They were appointed instrument makers to the Queen, Greenwich Observatory, and the British Meteorological Society
1853 When the Crystal Palace was re-erected in Sydenham, Negretti and Zambra became the official photographers of the Crystal Palace Company, which allowed them to photograph the interior and grounds of the new building. The firm made use of this access to produce a number of stereographs.
Between 1855 and 1857 Negretti and Zambra commissioned photographer Pierre Rossier to travel to China to document the Second Opium War. Although Rossier subsequently was unable to accompany to Anglo-French forces in that campaign, he nevertheless produced a number of stereographs and other photographs of China, Japan, the Philippines and Siam (now Thailand), which Negretti and Zambra published and that represented the first commercial photographs of those countries.
1856 Negretti and Zambra sponsored a photographic expedition to Egypt, Nubia and Ethiopia conducted by Francis Frith.
More than 500 stereographs of Frith's voyage were produced by the firm between 1857 and 1860.
Their patents included the process of enamelling the back of thermometer tubes, a feature which at the time they did not consider important, but which quickly became standard practice.
1857 they made a pressure-resistant deep-sea thermometer for Admiral Fitzroy
1859 The firm's 1859 catalogue described 2134 items and instruments and this range doubled a few years later.
1859 Moved to a larger workshop at 1 Hatton Garden
1863 They carried out improvements at Fitzroy's suggestion to make mercurial barometers withstand the concussion of naval guns.
1863 Henry Negretti took the first aerial photographs of London from a balloon.
1864 Negretti and Zambra (themselves) photographed Shakespeare's House, Stratford-on-Avon. A sepia photograph was then pasted onto card 4" × 2.5". This was then presented to visitors to the Crystal Palace to enable them to compare it with the model erected by Mr E. T. Parr in the Centre Transept. The card itself is headed "Crystal Palace April 23rd 1864." That year they also published a book, titled A Treatise on Meteorological Instruments, (which was reprinted in 1995).
1867 Moved to 103 Hatton Garden
1869 Moved to 38 Holborn Viaduct, as well as premises in Cornhill and Regent Street.
1892 Dissolution of the Partnership between Joseph Warren Zambra, Henry Paul Joseph Negretti, and Joseph Caesar Zambra, carrying on business as Merchants, at 11, Holborn-circus, London, and as Opticians and Optical and Scientific Instrument Makers, at 11, Holborn-circus and 45, Cornhill, London, at 122, Regent-street, Middlesex, and at the Crystal Palace, Sydenham, Kent, and elsewhere, under the style or firm of Negretti and Zambra, so far as regards Joseph Warren Zambra.
1908 Catalogue included various types of thermometer, barometer, binoculars, microscopes, ships compasses, mathematical instruments.
1910 Exhibited at the Physical Society's Exhibition
1914 Opticians and scientific instrument manufacturers; also foreign merchants and shippers. 
WWI Almost entirely engaged on production of various instruments for the Ministry of Munitions.
1920 at the request of the Air Ministry produced and patented a mercury-in-steel distance thermometer for taking oil and air temperatures in aircraft, which was the start of diversification into aircraft and industrial instruments.
Similar instruments developed for use in industrial processes, boiler and marine uses.
Other instruments were developed to meet Air Ministry requirements such as boost gauges, transmitting oil pressure gauges and transmitting fuel pressure gauges for use in aircraft.
1921 George Julius Zambra left Negretti and Zambra, a partnership with Henry Noel Negretti, Paul Ernest Negretti and Marcus William Zambra carrying on business as Opticians, at 38, Holborn Viaduct, London
1921 See the Telescopes Catalogue (List No. D. 2.), showing;
c1930s Negretti and Zambra (Environmental) Ltd., of Stocklake, Aylesbury, Bucks - makers of anemometers, anemographs, barometers, barographs, hygrometers, hygrographs, marine instruments, tadiation instruments, rain gauges, recording rain gauges, record cahrts, recording ink, nibs etc., registers, forms, sunshine recorders, thermometers, thermometer screens, thermographs.
1930 Another very important development was the hardened and tempered steel diaphragm for boost control of aero engines. Other instruments were electrical resistance thermometers and thermocouple pyrometers, pressure and draught gauges, also automatic control instruments. At the request of the Air Ministry and several prominent aero engine manufacturers, developed and patented a fuel flow-meter.
1935 Marcus William Zambra retired from the Partnership with Henry Noel Negretti and Paul Ernest Negretti, Scientific Instrument Manufacturers and Export Merchants, at 38, Holborn Viaduct, and 122, Regent Street, and Half Moon Works, Barnsbury, London
1937 Aircraft scientific instruments. 
1939 See Aircraft Industry Suppliers
WWII The Government provided a factory at Chesterfield for manufacture of aircraft instruments and boost controls, where 450 people were employed. Meanwhile the works in London were making other essential instruments. The Ministry of Aircraft Production also provided premises at Chobham, Surrey, where other production and research were carried out. The diaphragm boost controls were also manufactured in the U.S.A. under licence.
1946 Private company.
1947 Listed Exhibitor - British Industries Fair. Manufacturers of Industrial, Aeronautical and Meteorological Instruments. (Olympia, Ground Floor, Stand No. A.1076) 
1948 Company made public. Paul Ernest Negretti was chairman and managing director.
1950 Negretti and Zambra had 821 employees in Britain.
1961 Manufacturers of industrial, scientific, meteorological and aeronautical instruments and aero-engine controls. 1,200 employees. 
1964 In order to increase production and to safeguard future development purchased a modern factory at Aylesbury for all their production.
1987 Negretti Aviation won a contract to supply aircrew respirators to the US Marine Corps