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.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.