Put a sheet of
rubber over the mouth of the large bottle, draw the edge down over
the neck and wrap securely with a piece of string thus forming a
tightly stretched diaphragm over the top. When a finger is pressed
on the rubber the small bottle will slowly descend until the
pressure is released when the
[Illustration: Pressure Experiments]
small bottle wilt ascend. The moving of the small bottle is caused
by the pressure transmitted through the water, thus causing the
volume of air in the small tube to decrease and the bottle to
descend and ascend when released as the air increases to the
original volume.
This experiment can be performed with a narrow-necked bottle,
provided the bottle is wide, but not very thick. Place the small
bottle in as before, taking care not to have too much air in the
bottom. If the cork is adjusted properly, the bottle may be held
in the hand and the sides pressed with the fingers, thus causing
the small bottle to descend and ascend at will. If the small
bottle used is opaque, or an opaque tube such as the cap of a
fountain pen, many puzzling effects may be obtained.
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