Fill a tumbler with water and put a piece of writing-paper over the top. Hold the hand on the paper and quickly invert the tumbler, or turn it bottom upwards; then remove the hand, and the pressure of the air against the paper will keep the water in the tumbler. This is represented in [Fig. 12].
Fig. 12.
If a tumbler be filled with water in a bucket, and then raised bottom upwards until its edge is just below the surface of the water, it will remain full of water; why is this?
The pressure of the air on the water in the bucket, keeps the water in the tumbler.
If we use an iron pipe or a lead pipe, instead of a tumbler, will the pressure of the air keep the water in the pipe?
It will, the same as it keeps it in the tumbler.
How high will the air keep the water in the pipe?
It will keep the water to the height of thirty-four feet.
Why does the air keep the water up thirty-four feet?