Cartesian diver

noun

1. a glass vessel partially filled with water and covered with an airtight membrane, containing a hollow object that is open at the bottom and contains just enough air to allow it to float. Pressing on the membrane compresses the air in the vessel and forces water into the object, causing it to sink; releasing the membrane causes it to rise.

Example Sentences

By measuring the pressure that will keep the underwater Cartesian diver on the zero line, Dr. Prescott can weigh his captive amoeba at all stages of growth.

From Time Magazine Archive

When this "Cartesian diver" is properly weighted, it floats midway in a column of water, and slight changes in water pressure can make it sink or rise by compressing its bubble.

From Time Magazine Archive

Working with a powerful microscope, he picks one of them up with a hairlike suction tube and delicately transfers it to a minute cup on top of the Cartesian diver.

From Time Magazine Archive