Because the air can force water up a tube only to the height of thirty-four feet.
Does this valve move about in the pump-tube?
No; it remains fixed in one place.
Is this valve air-tight?
Yes; the lower valve or bucket in a pump must always be air-tight.
Where is the upper valve?
It is fastened on the end of a rod, which is attached to the pump-handle.
Does this valve remain fixed in one place?
No; it moves up and down when the pump-handle is moved.
Is the upper valve air-tight?