Original U.S. WWII Navy Marked Brass Compensated Aneroid Barometer by Short & Mason of London

Item Description

Original Item: Only One Available. A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, pressure systems and frontal boundaries.
An aneroid barometer is an instrument used for measuring air pressure as a method that does not involve liquid. Invented in 1844 by French scientist Lucien Vidi, the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. The evacuated capsule (or usually several capsules, stacked to add up their movements) is prevented from collapsing by a strong spring. Small changes in external air pressure cause the cell to expand or contract. This expansion and contraction drives mechanical levers such that the tiny movements of the capsule are amplified and displayed on the face of the aneroid barometer. Many models include a manually set needle which is used to mark the current measurement so a change can be seen. This type of barometer is common in homes and in boats. It is also used in meteorology, mostly in barographs and as a pressure instrument in radiosondes.
A barometer is probably the most important weather instrument to have on board. While all the others offer useful information, knowing the atmospheric pressure, and, more importantly, how it is changing over time, provides essential information about how weather systems affecting the ship are behaving.
Because atmospheric pressure changes with distance above or below sea level, a barometer can also be used to measure altitude. There are two main types of barometers used on ships: mercury and aneroid. This one appears to be a combination of the two with the mercury level located on the bottom of the face.
The condition is excellent with a lovely dark patina to the brass housing. The face glass is free of any cracks or scratches and just needs a good cleaning if you would wish to do so. All numbers and markings on the dial retain their original blackened color making them still very legible. The diameter of the face is 5 ¼” and the top still retains the hanging loop.
An excellent example of an early US Naval barometer. Comes ready for display and further research!
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