LEFT TO YOUR OWN DEVICES
'(<a href="http://www.j-archive.com/media/2008-04-09_J_10.jpg" target="_blank">Kelly of the Clue Crew gives the clue from a lab.</a>)  Stretch a balloon over a glass, secure with rubber bands, then place a straw on top & you have a simple <a href="http://www.j-archive.com/media/2008-04-09_J_10a.jpg" target="_blank">version</a> of this device that measures air pressure'
a barometer