How are a mercury barometer and a aneroid barometer alike and different?
mercury barometer (′mər·kyə·rē bə′räm·əd·ər)
(engineering) An instrument which determines atmospheric pressure by measuring the height of a column of mercury which the atmosphere will support; the mercury is in a glass tube closed at one end and placed, open end down, in a well of mercury. Also known as Torricellian barometer.
aneroid barometer n.
A barometer in which variations of atmospheric pressure are indicated by the relative bulges of a thin elastic metal disk covering a partially evacuated chamber.
Mercury barometer and aneroid barometer are used to measure air pressure. A mercury barometer uses a mercury column supported by air pressure and the length of the mercury column gives the value of air pressure. An aneroid barometer uses an evacuated corrugated metal canister that will expand and also contract depending on the changes to the air pressure present.