The electric egg lies at the intersection of two technologies: high
vacuum and high voltage. By the eighteen sixties vacuum
pumps, and induction
coils and electrostatic
machines (including Wimshurst
and Voss machines)
had developed to the point where it was possible to create an electrical discharge
in the residual gas between two small spheres in the evacuated space. Gassiot's
Shower is another example of an electrical discharge between two electrodes
in a near vacuum. Unlike Geissler
tubes, which are evacuated and sealed off, electric eggs are pumped out each
time, the valve closed, and the tube placed back on its foot for the demonstration.
The upper electrode can be slid up and down through a leather-lined and greased
packing to change the length of the discharge. With residual air, the glow is
bluish, but other gases and liquids can be introduced into the egg to give different
colors of discharge. Some of the eggs have hooks on the upper electrodes, to allow
them to be hung from one conductor of the high-voltage source.
The egg in the Amherst College Collection was made by E.
Ducretet and Company of Paris.
Note that the electric egg in the middle below is made from uranium glass,
with is also present in the Gassiot's
The left-hand example is by Apps of London, and is not a true electric
egg. A very similar piece is shown at a price of $6.00 in the 1856 catalogue
of Benjamin Pike, Jr. of New York, who may have imported the apparatus.
The electrodes are made of carbon, and adjusted until they almost touch.
After the globe is filled with chlorine gas, an electric arc is struck
between the electrodes, which glow red hot. The chlorine is unaffected
by the heating of the electrodes.
| The upper electric egg is at Bates College
in Maine, and was made by Chamberlain of Boston. This firm became Chamberlain
and Ritchie by 1854, which sets an upper bound to its age.
The lower example is from St. Mary's College in Notre Dame,
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