Geoscience Reference
In-Depth Information
of these streams or on whether or how the water returns to where the streams originated.
The earliest speculations on this problem, which were not of an obvious mythical nature
but based on observations, were probably those of the Greek natural philosophers.
14.2 Greek antiquity
The ancient Greeks are renowned for the large effort their natural philosophers made to arrive
at a rational explanation of the world within that same world, without animistic or direct
divine intervention. Inspection of their writings and other transmitted evidence indicates
that water and various aspects of the water cycle played a central role in their cosmology.
As seen in Hesiod's passage, the atmospheric phase of the hydrologic cycle was already
a common concept among the Greeks in pre-philosophic times (see also Brutsaert, 1982).
Therefore, it is mainly the evolution of their opinions on the origins of springs and rivers,
that will be examined in what follows.
14.2.1 The Presocratics
The earliest Greek philosophers who were active in the sixth and fifth centuries BCE are
customarily referred to as the Presocratics. Some of their writings were handed down to us
in the form of fragments and some were paraphrased by later writers. Among these natural
philosophers two competing theories prevailed on the origin of the water in springs, streams,
and other fresh water bodies. These are the seawater filtration theory, which was probably
the earlier of the two, and the rainfall percolation theory, which contains the essence of our
present understanding.
Seawater filtration theory
The basic idea of this theory is that seawater seeps upward through the Earth, loses its salt
by filtration and becomes the source of the springs and other surface waters (Figure 14.1).
The written evidence points to Hippon as the earliest proponent of this view. Hippon of
Rhegion, in what is now southern Italy, also called Hippon of Samos, was a contemporary of
Pericles, so he must have flourished around the middle of the fifth century BCE. His opinion
on the matter, in the only surviving fragment by him (Diels, 1961, p. 388) is formulated as
follows.
Indeed all drinking waters originate from the sea; for the wells from which we drink are not deeper
than the sea. So should the water not be from the sea, then from somewhere else. Now, the sea is deeper
than the waters. Thus whatever waters are above the sea, all originate from it.
This fragment is rather terse and not very explicit. However, it should be seen in light of the
fact that Hippon's other views were nearly identical with those of Thales, presented at least
a century earlier. The following passage by Theophrastos in his
Physical Opinions
(Diels,
1879, p. 475) is revealing.
Of those who say that the original principle (arche) is one and movable, whom he (Aristotle) calls
physicists, some contend that it is bounded; for instance, Thales of Miletos and Hippon, who appears
even to (have) become an atheist, said that water is the first principle, being led to this by the observation
of the phenomena; for heat thrives in moisture, dead matter dries out, the seeds of everything are moist,
and all food is succulent; and naturally each thing is nourished by that from which it originates. Water
is the principle of the moisture and the bond of everything. Therefore, they maintained that water is
the first principle of everything and that the earth evidently rests on water.
