Negretti & Zambra aneroid barometer. London 16092.

Circa 1900, London.

Fully working and in a good original condition.

Dimensions: 150.00mm high x 124.00mm wide x 60.00mm deep

The definition of aneroid is derived from Greek meaning without water but adopted in 19th French to embrace a broader definition of without liquid. Change in air pressure is measured through the movement of the ribbed circular chamber which contains a vacuum. A sprung arm attached to the chamber is connected to a light blued steel hand by a simple linkage involving a coiled fusee chain held in tension with a fine balance spring.

The silvered dial has painted numerals and descriptions of possible weather conditions in varying fonts but the numerals correspond to the length in inches of mercury pushed up in a glass tube with a vacuum at top first discovered by Galileo's pupil Torricelli.

The dial is protected by a bevelled edge glass with a central brass set hand and knurled set screw which enable one to compare the rate of change. A set screw located on the back allows the main hand to be adjusted.

Original lacquer remains in very good condition both externally and internally giving the whole barometer an attractive patina. Although portable the barometer can be hung on the wall by the round hoop at the top.

Negretti & Zambra formed a highly productive and successful partnership in 1850 developing a number of scientific and philosophical instruments. Improvements and advances in their instruments involved collaboration with eminent figures in the nascent science of meteorology such as Admiral Fitzroy and James Glaisher F.R.S. and led to eventual royal appointments.

http://www.freunde-alter-wetterinstrumente.de/files_pdf/negretti_cent.pdf

Dimensions: 150.00mm high x 124.00mm wide x 60.00mm deep

£240.00

   
Negretti & Zambra aneroid barometer. London 16092.