Tantalus' Cup
   Tantalus's Cup is based on the Intermittent Spring, shown at the left (from Elroy M. Avery, Elements of Natural Philosophy, (Sheldon, NY, 1885),  p.179).

   The system is a syphon. When the level of the water in the underground source rises to the top level of the channel leading to the outside world, the syphon begins to act. The water continues to flow until the level of the source falls to the mouth of the channel. The spring ceases to flow until the water level builds up to the top level of the syphon once more.
              Wittenberg University                             Harvard Unversity                                      Union College
 
   This dribble glass (to give it its common name) was sitting on a bench in a lecture demonstration room at the University of Texas in Austin when I visited in January 2003.





 The dribble glass at the right is at Hobart and William Smith Colleges in Geneva, New York.

REFERENCE: Thomas B. Greenslade, Jr., "Nineteenth Century Textbook Illustrations (VI), Intermittent Springs", Phys.Teach., 14, 173 (1976)

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