Meteorology   

and down is what fills rivers. Many of these form lakes in various

places (our sea is an instance of one of these), but all of them

come round again in a circle to the original source of their flow,

many at the same point, but some at a point opposite to that from

which they issued; for instance, if they started from the other side

of the earth's centre, they might return from this side of it. They

descend only as far as the centre, for after that all motion is

upwards. Water gets its tastes and colours from the kind of earth

the rivers happened to flow through.

But on this theory rivers do not always flow in the same sense.

For since they flow to the centre from which they issue forth they

will not be flowing down any more than up, but in whatever direction

the surging of Tartarus inclines to. But at this rate we shall get the

proverbial rivers flowing upwards, which is impossible. Again, where

is the water that is generated and what goes up again as vapour to

come from? For this must all of it simply be ignored, since the

quantity of water is always the same and all the water that flows

out from the original source flows back to it again. This itself is

not true, since all rivers are seen to end in the sea except where one

flows into another. Not one of them ends in the earth, but even when

one is swallowed up it comes to the surface again. And those rivers

are large which flow for a long distance through a lowying country,

for by their situation and length they cut off the course of many

others and swallow them up. This is why the Istrus and the Nile are

the greatest of the rivers which flow into our sea. Indeed, so many

rivers fall into them that there is disagreement as to the sources

of them both. All of which is plainly impossible on the theory, and

the more so as it derives the sea from Tartarus.

Enough has been said to prove that this is the natural place of

water and not of the sea, and to explain why sweet water is only found

in rivers, while salt water is stationary, and to show that the sea is

the end rather than the source of water, analogous to the residual