Electric Egg
   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.

                  Amherst College                                Glasgow University                             Smithsonian Institution

Note that the electric egg in the middle below is made from uranium glass, with is also present in the Gassiot's Shower cup.
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.

              Dartmouth College                               Wittenberg University                             Dartmouth College
   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, Indiana. 

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