Barometer tube (glass) for demonstrating atm. Pressure

Barograph, a barometer which can measure and record the atmospheric pressure as part of weather forecasting. This is an aneroid barometer in which changes in atmospheric pressure causes a bellows- like vacuum chamber (at centre) to expand or contract. This deformation causes a pointer to move around the face of the graph paper to reveal the atmospheric pressure. The barometer here has been calibrated in units of inches of mercury. High pressure generally indicates a period of dry weather, whilst low pressure weather systems tend to be rainy.