Underground Rivers - University of New Mexico

Chapter 10 -- Geophysical, Pnuematic and Electromagnetic Engines
Because rain clouds often appear in conjunction with wind gusts, da Vinci believed that a vacuum
is formed by the condensation. Actually, it's the aerodynamic drag of falling droplets that draws
air downward. Variation of atmospheric pressure indeed explains the paths of frontal rainstorms,
but the same can't be said for the flow of liquid water.
Gregor Reisch (1467-1525) was an
intellectual of the Humanist era. His chief
work was the Margarita Philosophica
(1504), an encyclopedia of knowledge for
youthful students, the World Book of his
day.
Following is his explanation of the role of pressure, or more specifically, negative pressure.
Within the earth as we have shown there are many open spaces and passages, into which
(since there can be no such thing as a vacuum) vapors are drawn up from the earth and
condensed into drops of water which unite to from rills, which running down to lower levels
issue into the open air as springs.
Reisch then went on to assert that the condensation results in a new vacuum which in turn draws
up more vapor. In short, the water sucks itself up.
The plungers in the illustration from Fludd's
Philosophia Mosaica (1638) suggest a
pneumatic causation for subterranean flow,
though in this case it seems to be at global
scale.
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