Take a piece of dry and warm wood into a dark room, suddenly rend
it asunder, and a flash of light will be perceived. The same effect
may likewise be produced by suddenly snapping asunder a stick of
sealing-wax in the dark.
Or, break a Prince Rupert’s drop, and electrical light will pervade the
whole, so that its form will be distinctly visible in the dark. The
light will appear, even if the experiment be made under water.