Book 30, Question 93
What can a hand pump teach us about air pressure?
A hand pump has a handle that moves a piston up and down inside a pipe.
Lifting it makes a partial vacuum, and the push of the air outside the well pushes water up the pipe. This works only to about 10 meters (33 feet) deep, because air pressure can only push water so far. Deeper wells need pumps that push from below.