The Columbia Encyclopedia, Sixth Edition. 2001-07.
barograph
instrument used to make a continuous recording of atmospheric pressure. The pressure-sensitive element, a partially evacuated metal cylinder, is linked to a pen arm in such a way that the vertical displacement of the pen is proportional to the changes in the atmospheric pressure. The pen traces a record of pressure versus time on a chart, which is mounted on a drum rotated by a clockwork. Each chart usually provides one week’s record. See barometer.
