Let me preface this by saying that I'm no scientist, so I can't address the
specifics regarding the science of fluid dynamics applicable to what I think
is more generally known as a Hero's Fountain.  Your correspondent's question
is interesting, because it goes to a question I had during a recent visit to
Monticello:  being up on a mountain and  not seeing any nearby streams, how
did Jefferson ensure that there would be water available during times of
insufficient rainfall?  (If you have any input you could supply on that
question, I'd be interested--the guide simply pointed to the cisterns by the
house.) Perhaps Jefferson experimented with the concept of the Hero's
Fountain, an experiment that is often a staple of high school
physics classes.  A Hero's Fountain is one way to get water from a lower
level to higher level, as it seems would have been required at Monticello.

The high school experiment I remember is demonstrated (with a drawing) at
the URL:

http://hawthorne.omsi.edu/teachers/sln/ww/background/science/basics/Hero.htm
l

(In case it got truncated, its "Hero.html" at the end of the URL.)

To do the experiment, you need a funnel, two bottles, and 3 pieces of
tubing. For those of us who don't want to relive our high school physics
class, I'll give the text:

Briefly, a Hero's Fountain uses both gravity and pressure to create a
continuous fountain.  Begin the fountain by pouring water into the funnel.
Gravity pulls the water down the first tub and into the lower bottle.
Increasing the amount of water in the lower bottle increases the air
pressure in that bottle and in the second tube. The lower bottle is, in
effect, "blowing" air into the upper bottle. This causes the air pressure to
increase in the upper bottle, forcing water up the third tube. The water
eventually pours out the top of the third tube, back into the funnel, and
the cycle starts again. As long as you put in enough water, the Hero's
Fountain will continue, using gravity and pressure to operate until there is
no more water in the upper bottle.

Jill M. Myers
Montgomery Village, MD
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