About Glass Barometers

Everyone talks about the weather but nobody does anything about it, at least according to the old adage. While we may not be able to do anything to control the weather, scientists have made great strides in predicting weather patterns. Computer enhanced radar programs including weather imaging satellites and Doppler radar help meteorologist to more accurately forecast storms, severe weather and even pleasant conditions. Past generations didn't have the technology that exists today. In the good old days our forefathers relied on glass barometers to predict a change in the weather.

History

A 17th century physicist and mathematician, Evangelista Torricelli, is credited with inventing the barometer. Following the advice of his mentor, Galileo, Torricelli experimented with mercury in a vacuum tube and observed the changes in the height of the mercury caused by changes in the atmospheric pressure. Known as Terricelli's Tube, the first barometer was introduced in 1644 AD. No one is sure when the glass barometer, typically filled with water, was invented, but the the German philosopher, Johann Wolfgang von Goethe, wrote about them around the turn of the 18th Century and they are frequently referred to as Goethe's barometer.

Significance

The ability to predict the weather has enormous significance, particularly in the agrarian societies of past centuries where preparation for impending storms could mean the difference between a prosperous year and starvation. The glass barometer was a simple yet elegant invention that allowed common farmers to predict with acceptable accuracy whether a storm was brewing, or if they should prepare for planting or harvest. Today's farmers rely more on their local forecast than their glass barometer, but these devices are still a valuable aid in teaching children the principles of atmospheric pressure.

Function

A glass barometer is typically made of blown glass and resembles a teapot in shape. It has a wide body and a narrow spout into which colored water is poured. The air which is trapped inside the glass by the water provides a constant pressure. When the outside atmospheric pressure increases, indicating fair weather, the high pressure forces the water further down the spout. When a low pressure system approaches, the lesser pressure allows the water to rise in the spout.

Considerations

Glass barometers can predict changes in the weather with surprising accuracy from 8 to 12 hours in advance of the change. If the water rises slowly to the top of the spout there could be a storm headed your way within the next 24 hours. If the water rises quickly to the top there is a good chance that a local storm is on its way and if the water bubbles over it will probably hit within a few hours. If the water in the spout maintains its level half way up you can expect fair weather. Of course a storm can always change its course.

Benefits

With the advanced weather forecasting tools available to professional meteorologists, the glass barometer is no longer necessary for predicting the weather. It is, however, a delightful and useful decorative addition to many homes. It has the added benefit of being a wonderful teaching aid for children and a fitting reminder of a time when farmers and sailors relied on such devices along with weather vanes, thermometers, and a weather eye on the sky to predict impending storms.

Resources

• A History of Weather Instruments