- A barometer is an instrument used to measure atmospheric pressure, which can be an indicator of weather patterns, storms, tornadoes, hurricanes, snow, rain and other events. The barometer was used by sailors, farmers, citizens and traders to measure atmospheric changes and predict weather occurrences which might affect their routes or investments.
- Barometers generally come in three types: mercury, water and aneroid. Mercury barometers are long cylindrical tubes with mercury inside, which have a closed end and an open end. The open end remains submerged in a container of mercury, and the level of mercury rises or falls with the changes in atmospheric pressure. Water barometers are most often teapot-shaped and made from glass, with a large central container and one open spout. The mouth of the spout is the only opening in the water barometer; as the air changes, the water moves up or down, sometimes even overflowing the spout. Aneroid (fluidless) barometers utilize a small box, usually made from an alloy of beryllium and copper, which expands or contracts with changes in air pressure. This causes springs and levers to move and adjust the levels annotated on the face of the barometer.
- It is generally agreed that an assistant of Galileo's, Evangelista Torricelli, invented the first barometer in 1644, although some reports attribute its creation to an unintentional project of Italian scientist Gasparo Berti in the early 1640s. It is known that Torricelli was the first scientist to create a sustained vacuum and to realize that the movement of liquid within a vacuum was in response to air pressure changes. It was through his experiments with creating vacuums that he discovered this strange property of liquid (either water or mercury). His first barometric invention, what he called "Torricelli's tube," was the first mercury barometer. Water barometers, also known as storm glasses or weather glasses, came onto the written record around 1700, though it is not known when or where they were invented. These were referenced first by Goethe and are sometimes also called "Goethe's barometers." Over the next few centuries, various scientists made refinements to and additions for the barometer style developed by Torricelli. One of these was Lucien Vidie, who in 1843 created the first fluidless barometer, called an aneroid barometer. Another was Admiral Robert FitzRoy, noted for his captainship of the HMS Beagle, which carried Charles Darwin on his famous voyage. FitzRoy also created the "Admiral Fitzroy" barometer, a model which is still in use today, to incorporate the methods of weather knowledge he collected as the ship's captain.
- The significance of the barometer's invention and its influence on history cannot be underestimated. The barometer was developed in tandem with the first true studies of air pressure and weather prediction. It was valuable to a wide range of occupations, including farming, sailing, traveling and trading, and contributed an enormous amount of knowledge to the recorded weather history of the world. Weather studies today still rely on the principles discovered through the creation of the barometer.
- Mercury, an element used in many early barometers, is now known to be a dangerous chemical and should not be ingested, touched, or allowed to touch surfaces in your home or lab outside of its container. Its toxicity when soluble is high and can be poisonous.
