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"The degree to which the air has been exhausted from a closed vessel in which there is a partial vacuum is measured by the height to which a mercurial column in a vertical tube, whose top is connected to the vessel, will rise under the pressure of the atmosphere." —Hallock 1905

Barometer Measuring Pressure of a Partially Evacuated Vessel

"The degree to which the air has been exhausted from a closed vessel in which there is a partial vacuum…