| The bladder demonstration is a variant of the
Palm Glass demonstration. Instead
of atmospheric pressure holding a hand on the top of an evacuated glass
jar, open at both ends, a piece of animal bladder is tied over the upper
opening of the glass, and the glass exhausted until the membrane bursts
inward with a bang. This seemingly simple effect is mentioned in the majority
of nineteenth century textbooks.
The apparatus I photographed at Washington and Lee University in Lexington, Virginia in the early 1980s. It had clearly been waiting since its last use sixty or seventy years before to be rediscovered.