Atmospheric pressure, or simple air pressure is constantly changing. It can't be seen or felt. Weather forecasters illustrate this natural phenomenon rather graphically on T.V. screens with dramatic high and low pressure systems moving across your region. These pressure systems affect your weather. Barometers are designed to sense the slighest change in air pressure and display the change in pressure on a dial. Forged brass case. 4 1/2" dial. Overall dimensions  5 3/4" diameter x 3 1/2" deep. Shown with optional traditional mahogony base. Can also be wall mounted. This barometer matches the Chelsea quartz or wind-up shipstrike clocks.