Barometers

A barometer measures atmospheric pressure or the amount of pressure in the air. Barometric pressure changes as weather changes.

The original barometer was developed in 1643 by Evangelista Torricelli. He used an inverted glass tube with one open end which he placed in a container of water. Torricelli watched as the water would rise inside the glass tube and concluded that the rising amount of air pressure would push down on the water, forcing it up into the tube. The theory has advanced through the years since, making it a widely used predictor of upcoming weather conditions.

Water based barometers work much like Torricelli's original design, with a few updates. Created by Lucien Vidie, water barometers feature a teardrop glass container of water with a spout pointing up. This version can be duplicated in homemade barometers. Mercury based barometers use the same principles, but replace the water in the glass tube with mercury, as it can react better to pressure changes. Aneroid barometers use a spring which expands and compresses based on atmospheric conditions, relaying that change to a pointer, which measures the reading on a dial.

• Yahoo! Message Boards: Barometer Pressure

• Yahoo! Groups: Barometer Restoration Group

• Antique Scientific Instrument News: Mercury Regulations and Antique Barometer Collecting in the US

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