number of rivers. Maeotis flows into Pontus and Pontus into the
Aegean. After that the flow of the remaining seas is not so easy to
observe. The current of Maeotis and Pontus is due to the number of
rivers (more rivers flow into the Euxine and Maeotis than into the
whole Mediterranean with its much larger basin), and to their own
shallowness. For we find the sea getting deeper and deeper. Pontus
is deeper than Maeotis, the Aegean than Pontus, the Sicilian sea
than the Aegean; the Sardinian and Tyrrhenic being the deepest of all.
(Outside the pillars of Heracles the sea is shallow owing to the
mud, but calm, for it lies in a hollow.) We see, then, that just as
single rivers flow from mountains, so it is with the earth as a whole:
the greatest volume of water flows from the higher regions in the
north. Their alluvium makes the northern seas shallow, while the outer
seas are deeper. Some further evidence of the height of the northern
regions of the earth is afforded by the view of many of the ancient
meteorologists. They believed that the sun did not pass below the
earth, but round its northern part, and that it was the height of this
which obscured the sun and caused night.
So much to prove that there cannot be sources of the sea and to
explain its observed flow.
We must now discuss the origin of the sea, if it has an origin,
and the cause of its salt and bitter taste.
What made earlier writers consider the sea to be the original and
main body of water is this. It seems reasonable to suppose that to
be the case on the analogy of the other elements. Each of them has a
main bulk which by reason of its mass is the origin of that element,
and any parts which change and mix with the other elements come from
it. Thus the main body of fire is in the upper region; that of air
occupies the place next inside the region of fire; while the mass of
the earth is that round which the rest of the elements are seen to