Underground Rivers - University of New Mexico

Chapter 7 -- The Concept of Circulation
the sun draws up the water in the form of moist vapor, which afterwards falls down in thick
heavy rain.
And these are carried by the winds from one region to another, until at last their density gives
them such weight that they fall in thick rain. But if the heat of the sun is added to the power of
the element of fire, the clouds are drawn up higher and come to more intense cold, and there
become frozen and so produce hail.
And here, da Vinci is at his best.
The element of fire by its heat always draws to itself damp vapors and thick mists as opaque
clouds which it raises from seas as well as lakes and rivers and damp valleys; and these being
drawn by degrees as far as the cold region, the first portion stops, because heat and moisture
cannot exist with cold and dryness; and where the first portion stops, the rest settle, and thus
one portion after another being added, thick and dark clouds are formed.
At times it is bathed in the hot element and dissolving into vapor becomes mingled with the air,
and drawn upwards by the heat it rises until it reaches the cold region and is pressed closer
together by its contrary nature, and the minute particles become attached together.
We'll return to more of da Vinci's circle-driving inspirations in the chapter to follow, but before we
begin to think mechanically, let us look ahead regarding a darker view of circulation.
Robert Hooke (1635-1703), whose name is applied to the law of elasticity, was the son of a
minister who “died by suspending himself.” From Hooke's dismally-titled The Earth Grows Old
and Less Fruitful (1705),
Nature... is, as it were, a continual circulation. Water is rais'd in Vapors into the Air by one
Quality and precipated down in drops by another, the Rivers run into the Sea, and the Sea
again supplies them. Generation creates and Death destroys. Winter reduces which Summer
produces... All things almost circulate and have their Vicissitudes.
It's a glum Ecclesiastes 1:7 which today we would call it the Second Law of Thermodynamics.
The Perception of Precipitation Insufficient to Sustain Streamflow
In beginning of this chapter, we noted a flawed perception, that precipitation is less than
streamflow. No free-thinker standing on the banks of a mighty waterway on a drizzly
Renaissance day thought other than, "Flumen est maioribus quam pluvia." The river flows more
than the rain.
Were water not circulatory -- if water simply came into existence as needed -- the system would
have little need for an underground conduit. And if nature didn't need the latter, there would be
no need for a subterranean resource to supply the underground river.
But as the rivers flow full, there must be the unseen replenishment, and thus there must be the
deeper source.
By 1500, Aristotle, not Plato, was the designated pre-Christian philosopher, but Plato's Tartarean
abyss yet had reason to exist.
And once again we note that it's hard to keep a good story down.
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