| Hero's Fountain is a very splashy and attention catching
The fountain is primed for use by filling the top and bottom reservoirs half full of water. Water is also poured into the pan at the top until the tube running from the pan to the bottom reservoir is full of water. The fountain then commences to play, and runs until all of the water in the top pan has run down into the bottom reservoir. The first time that the fountain is demonstrated it has all the appearances of a perpetual motion machine; it takes a sharp-eyed student to see that the height of the jet of water of constantly decreasing.
The operation depends on the fact that the weight of the water in the pan and in the pipe from the pan to the lower reservoir compresses the air in this reservoir. The other pipe connects the two reservoirs, and makes the pressure in the upper reservoir essentially the same as the lower reservoir. The extra pressure on the surface of the water in the upper reservoir forces the water up the slender tube leading from it to the nozzle, producing the fountain. It is easy to show that if this tube were long enough, the water would rise in it until its height above the surface of the water in the pan is just equal to the distance between the water levels in the two reservoirs.
REFERENCE: Thomas B. Greenslade, Jr., "Nineteenth Century Textbook Illustrations,
XLI. Hero's Fountain", Phys. Teach.
20, 169-70 (1982)
| In his 1983 book describing the apparatus in the
Garland Collection at Vanderbilt University, Prof. Robert T. Lagemann wrote:
"Some of the apparatus of the nineteenth century, as does some of the twentieth
century as well, had its origins in antiquity. Pneumatic devices from the
Alexandrine School provide a number of examples. If in that day they were
often devices meant for the mystification of the layman, and the philosopher
too, by the nineteenth century they became understandable in terms of the
concepts of the nature of a gas and in reconstructed form could be used
to demonstrate their new principles.
Hero's fountain derives its name from its inventor, Hero (or Heron), who lived in Alexandria circa 120 B.C.
It is described in his book Pneumatica in which Hero describes a number of appliances invented by himself and by a predecessor named Ctesibuis."
This example in the Garland Collection stands 1.05 m high.