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they are flowing their water forms a compact mass； but when it arrives
at a vast wide place it quickly and imperceptibly evaporates。
But the theory of the Phaedo about rivers and the sea is impossible。
There it is said that the earth is pierced by intercommunicating
channels and that the original head and source of all waters is what
is called Tartarus…a mass of water about the centre； from which all
waters； flowing and standing； are derived。 This primary and original
water is always surging to and fro； and so it causes the rivers to
flow on this side of the earth's centre and on that； for it has no
fixed seat but is always oscillating about the centre。 Its motion up
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
matter of all food； and especially liquid food； in animal bodies。
3
We must now explain why the sea is salt； and ask whether it
eternally exists as identically the same body； or whether it did not
exist at all once and some day will exist no longer； but will dry up
as some people think。
Every one admits this； that if the whole world originated the sea
did too； for they make them come into being at the same time。 It
follows that if the universe is eternal the same must be true of the
sea。 Any one who thinks like Democritus that the sea is diminishing
and will disappear in the end reminds us of Aesop's tales。 His story
was that Charybdis had twice sucked in the sea： the first time she
made the mountains visible； the second time the islands； and when
she sucks it in for the last time she will dry it up entirely。 Such
a tale is appropriate enough to Aesop in a rage with the ferryman； but
not to serious inquirers。 Whatever made the sea remain at first；
whether it was its weight； as some even of those who hold these
views say （for it is easy to see the cause here）； or some other
reason…clearly the same thing must make it persist for ever。 They must
either deny that the water raised by the sun will return at all； or；
if it does； they must admit that the sea persists for ever or as
long as this process goes on； and again； that for the same period of
time that sweet water must have been carried up beforehand。 So the sea
will never dry up： for before that can happen the water that has
gone up beforehand will return to it： for if you say that this happens
once you must admit its recurrence。 If you stop the sun's course there
is no drying agency。 If you let it go on it will draw up the sweet
water as we have said whenever it approaches； and let it descend again
when it recedes。 This notion about the sea is derived from the fact
that many places are found to be drier now than they once were。 Why
this is so we have explained。 The phenomenon is due to temporary
excess of rain and not to any process of becoming in which the
universe or its parts are involved。 Some day the opposite will take
place and after that the earth will grow dry once again。 We must
recognize that this process always goes on thus in a cycle； for that
is more satisfactory than to suppose a change in the whole world in
order to explain these facts。 But we have dwelt longer on this point
than it deserves。
To return to the saltness of the sea： those who create the sea
once for all； or indeed generate it at all； cannot account for its
saltness。 It makes no difference whether the sea is the residue of all
the moisture that is about the earth and has been drawn up by the sun；
or whether all the flavour existing in the whole mass of sweet water
is due to the admixture of a certain kind of earth。 Since the total
volume of the sea is the same once the water that evaporated has
returned； it follows that it must either have been salt at first
too； or； if not at first； then not now either。 If it was salt from the
very beginning； then we want to know why that was so； and why； if salt
water was drawn up then； that is not the case now。
Again； if it is maintained that an admixture of earth makes the
sea salt （for they say that earth has many flavours and is washed down
by the rivers and so makes the sea salt by its admixture）； it is
strange that rivers should not be salt too。 How can the admixture of
this earth have such a striking effect in a great quantity of water
and not in each river singly？ For the sea； differing in nothing from
rivers but in being salt； is evidently simply the totality of river
water； and the rivers are the vehicle in which that earth is carried
to their common destination。
It is equally absurd to suppose that anything has been explained
by calling the sea 'the sweat of the earth'； like Empedicles。
Metaphors are poetical and so that expression of his may satisfy the
req