The Weather Glass - The Farmer's and Sailor's Barometer
The History of the Barometer: Part 2
Mercury has always been the liquid of choice in barometers. But, with some ingenuity, water still works.
The concept of Air Pressure arrived at almost the same
time as the invention of the mercury barometer by Evangelista
Torricelli - it was virtually impossible to have one without
And Part 1 of The History of the Barometer
dealt with the refinement of the mercury barometer and the
early use of the barometer and changes in air pressure in
That caught the attention of the scientific fraternity, but more
practical and probably less wealthy people had another way of
predicting the weather.
The Weather Glass
Around the time of the barometer's invention, a simple device
called a Weather or Storm Glass was developed, although
we don't know by whom. The German philosopher Goethe wrote of
them around 1700, and they are sometimes referred to as Goethe's
barometer. Other names are Water Barometer and
The weather glass is a teapot like container, made of blown
glass, with a wide body and a thin spout which is the only
opening to the larger part of the weather glass. It is filled
with water, preferably colored, to a little above the connection
between the body and the spout.
Rising air pressure will push the liquid back down the spout,
whereas falling pressure will cause the water to rise in the
spout, even to the point where it overflows.
The weather glass was a useful predictive tool for farmers and
sailors, as a falling level in the spout indicated increasing
pressure and generally fine weather, and the opposite suggested
approaching rain and storms. The severity of the approaching
bad weather was indicated by the rate of change, and by a rise
in the level to the point of overflow.
This was a useful rule of thumb, but it is not known when the
connection to changes in air pressure was made.
The weather glass was a fine forecasting tool, particularly
when used with a weathervane and observation of the skies.
Its problem was that it couldn't be reliably calibrated and
it was almost impossible to compare one weather glass to
another. Other problems exist with using water to measure
air pressure - evaporation and freezing.
Weather glasses are still made today, mainly for decoration, and
make an excellent companion for a home weather station or
analog barometer. Amazon
has quite a good range from associated suppliers, while Boater's World has an attractive weather glass as well
as many modern barometers.
In contrast to weather glasses, the advantage of a mercury
barometer was that it was actually measuring something, and
the measurements were easy to duplicate in other instruments.
So there's a good place to step away from the history of the
barometer. A lot of development took place over the next 200
years, particularly in surveying, where it was used as an
altimeter, and in various navies.
But the problem with the difficulty of using and transporting
a large instrument with a mercury reservoir was never resolved.
The next article reveals where, when and how the next breakthrough
in the history of the barometer came. It deals with the Aneroid Barometer, with several
other offshoots thrown in. Ever thought of using a leech
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