Barograph

A barograph records air pressure on a rotating drum by amplifying pressure change through aneroid capsules. The capsules, which have a vacuum inside, expand and contract with changes in pressure. Multiple capsules amplify the pressure changes as does the arm extending from the capsules which traces the pressure by using an ink-filled nib on the end of the arm. The ink is drawn to the paper by capillary action - much like ink flows from a quill pen.

The barograph below was manufactured by Taylor Instruments. It is a Weather-Hawk Stormoscope Barometer No. 6450. The year this instrument was manufactured is unknown (so far) but they were available at least in the late 1960s and 1970s. There was also a thermograph version that measured temperature.

Barographs have been superseded by computer displays able to trace pressure change without using ink and paper. Computer systems can also use the pressure data in calculations. Barographs require an observer to read the trace to determine the date and time of the reading. Despite the drawbacks, barographs are still manufactured today and are mostly used for display purposes. Many come in exquisite wood cases and are displayed in cut glass panes. The first barograph was apparently made in the 1760s.

A barograph is a prized possession. Even though there are better ways to record pressure change there is nothing like a high quality barograph to grace a display case. They have the added benefit of letting us see pressure changes as they happen. If you like to do a little forecasting you can also use pressure change with other information, like clouds and wind to make a simple forecast. There is nothing like first-hand learning to encourage someone to get engaged with the world around them.