Underground Rivers - University of New Mexico

Less astutely, Lucretius noted,
Chapter 11 -- Straining the Salt
Since the earth has a porous body, and it is joined together with the sea, girdling its shores all
around, it is necessary that as the flow of water comes from the land into the sea, so also it
should ooze into the land from the salt sea; for the pungency is strained off, and the substance
of the water oozes back, and all meets in a moving mass of sweet along the path which was
once been cut for it in its liquid course.
The science is Roman -- to put it positively -- but as "ooze into the land" is poetic, we'll grant a
schematic of squeezed mud.
Springs
Ocean
Fifteen centuries later, even Athanasius Kircher (1602-1680), whom we met in Chapter 8, never
shy with answers, was perplexed by the oceans. According to Bishop Richard Watson's
Chemical Essays (1781-1787),
Father Kircher, after having consulted three and thirty authors upon the subject, could not help
remarking, that the fluctuations of the ocean itself were scarcely more various then opinions of
men concerning the origin of its saline impregnation.
But Why, Then, are Springs Not?
We need only consult Aristotle.
As fresh water is lighter than saltwater, the former properly seeks its natural place above the
latter by rising, though the philosopher himself wouldn't have defined "lightness" in terms of
physical measurement. That dissolved salt doesn't settle within the liquid, leaving a fresh upper
stratum, was pragmatically recognized by the Greeks, but Aristotle and his followers wouldn't
have conditioned the voracity of philosophical truth on fallible physical verification. Fresh seeking
fresh and salt seeking salt, the philosopher would have determined.
The practicality of subterranean salt separation aside, any desalination scheme poses a
consequent question. What becomes of the residue?
In the short run, we might expect the formation of salt beds, a geological formation familiar to the
ancients. In the long run, however, there's only so much subterranean space to store the
byproduct.
In his Notebook entry "Refutation of the Pliny's Theory of the Saltness of the Sea," da Vinci
(1452-1519) ponders Pliny. We'll break da Vinci's thoughts into proposition and refutation.
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