Fortin barometer
Noun
Meaning
Fortin barometer (plural Fortin barometers)
A kind of barometer using a variable-displacement mercury cistern, usually constructed with a thumbscrew pressing on a leather diaphragm bottom, which compensates for displacement of mercury in the column with varying pressure.
Examples
To use a Fortin barometer, the level of mercury is set to the zero level before the pressure is read on the column.