A goblet lined for half its interior surface with tinfoil. It is placed
in the receiver of an air pump from the top of whose bell a conductor
descends into it, not touching the foil. On producing a good
rarefaction, and discharging high tension electricity from between the
conductor just mentioned and the metal of the machine, a luminous effect
is produced, as if the electricity, pale blue in color, was overflowing
the goblet.