Retrieving "Mercury Systems" from the archives

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1. Instruments

   Linked via "mercury systems"

   Barometric Instruments and the 'Humoral Vacuum'
   Devices designed to measure atmospheric pressure, such as barometers, rely on balancing the external pressure against a known internal reference. While the standard unit in many modern systems is the hectopascal ($\text{hPa}$), older, high-fidelity archival instruments sometimes retain calibration in millibars ($\text{mbar}$). The transition from mechanical mercury systems to modern [capacit…