The paper "Even if a Mercurial Barometer Could Be Designed So That It Was Not So" is a great example of an essay on environmental studies. Atmospheric pressure is defined as the weight of a column of the atmosphere with a given cross-sectional area. Atmospheric pressure can be measured with the help of a mercurial barometer. Even if the instrument could be designed so that it was not so bulky and fragile, it would not work well in an airplane. The purpose of this paper is to discuss the above statement and to investigate alternatives to this type of barometer.
The mercurial barometer (Fig. 1) measures atmospheric pressure accurately, but its use is restricted to the laboratory or observatory. Even a modified, less bulky form of the instrument would not work well in an airplane because the fragile instrument carrying mercury has to be kept upright, to maintain a level surface of the mercury reservoir. Further, if the reservoir were to get ruptured, the leaking mercury can prove to be toxic. Alternative forms of instruments to measure atmospheric pressure may be used successfully in airplanes.
The aneroid barometer (Fig. 2) which works without liquid, operates on differences in air pressure between the atmosphere and a closed vessel, an aneroid cell. The aneroid barometer is a closed container with a partial vacuum. It is strong but flexible, not collapsing under pressure but sufficiently flexible to change in shape accurately according to changes in the atmospheric pressure acting down on it. The change in shape of the aneroid barometer caused by atmospheric pressure is recorded by the attached indicator, showing the pressure value.
Though the aneroid barometer does not measure atmospheric pressure as accurately as the mercurial barometer, its main advantage is that it is small and hardy and can be used in an aircraft. Moreover, the aneroid barometer is capable of withstanding strong g-forces caused by atmospheric turbulence and aircraft maneuvering. More recent developments include the digital pressure transducer (Fig. 3), with altimeter settings which are used in automated service observation stations for measuring atmospheric pressure. These instruments may also be used in airplanes and for other operations since they have certain significant advantages: accuracy, high sampling rate, robust construction, and small size.
This paper has highlighted the most suitable instruments for measuring atmospheric pressure in airplanes. For this purpose, the better alternatives to the traditionally used mercurial barometer are the aneroid barometer and digital pressure transducers.