Pocket barometer compendium having silvered and engraved barometer dial with calibrations from 21–31 inches of mercury, outer rotating altitude ring from 0-10,000 feet. The upper portion marked “Cartwright & Son,” the lower “Preston” and “Compensated.” Blued-steel pointer, bevelled glass. Drum form case with suspension ring and compensation port, with adjuster at 7 o’clock. 1¼” capsule with coil spring-tensioned movement, bimetallic compensation.
The verso with compass having mother of pearl Singer’s Patent floating card, with cardinals and intercardinals, transit lock with suspension loop. The circular mercurial thermometer set on a gilt register with calibrations in Fahrenheit having a range from -10 to 160 degrees. The whole presented in a good quality purple velvet and silk-lined brown moroccan leather over wood twin-lidded travel case with button releases.
Presented in very good original condition, the case retaining virtually all its original gilt lacquered finish, working well with good sensitivity and transition. The compass finds north easily, the transit lock works well, the thermometer reads correctly. The travel case in similarly fine condition.
The movement tensioned with the early coil spring pattern is interesting since the C-spring had been widely adopted – however, the C-spring was more easily fitted to larger instruments as it required a certain amount of vertical case space. Negretti & Zambra reverted to the coil spring in a bid to reduce the overall depth of the instrument. Later production saw the development of lower profile C-springs which then became universal to all instruments of this type.
These compendia are becoming increasingly difficult to find and must now be considered very scarce in this condition. A well-recommended collector’s piece.
Negretti & Zambra, founded in 1850 as makers of scientific instruments, were the most prolific and leading makers of all types of barometers during the second half of the 19th century. The partnership exhibited at the Great Exhibition at the Crystal Palace in 1851 and won a Prize Medal. Negretti & Zambra held the appointment of instrument-makers to Her Majesty Queen Victoria, Prince Albert and Edward VII, the Royal Observatory and the British Admiralty (see Banfield, Edwin, Barometer Makers and Retailers, 1660-1900).
G. Cartwright & Son, opticians, working from Fishergate, Preston, was established in 1820 and continued into the 20th century.
Dimensions: 3″ high x 1½” wide
Stock No: CP0425