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1
LET us explain the
nature of the
sea and the reason why such a large
mass of water is salt and the way in which it originally came to be.
The old writers who invented theogonies say that the sea has
springs, for they want
and sea to have foundations and roots
of their own. Presumably they thought that this view was grander and
more impressive as implying that our earth was an important part of
the universe. For they believed that the whole world had been built up
round our earth and for its sake, and that the earth was the most
important and primary part of it. Others, wiser in human knowledge,
give an account of its origin. At first, they say, the earth was
surrounded by moisture. Then the sun began to dry it up, part of it
evaporated and is the cause of
winds and the turnings back of the
sun and the
moon, while the remainder forms the sea. So the sea is
being dried up and is growing less, and will end by being some day
entirely dried up. Others say that the sea is a kind of sweat exuded
by the earth when the sun heats it, and that this explains its
saltness: for all sweat is salt. Others say that the saltness is due
to the earth. Just as water strained through ashes becomes salt, so
the sea owes its saltness to the admixture of earth with similar
properties.
We must now consider the facts which prove that the sea cannot
possibly have springs. The waters we find on the earth either flow
or are stationary. All flowing water has springs. (By a spring, as
we have explained above, we must not understand a source from which
waters are ladled as it were from a vessel, but a first point at which
the water which is continually forming and percolating gathers.)
Stationary water is either that which has collected and has been
left standing, marshy pools, for instance, and lakes, which differ
merely in size, or else it comes from springs. In this case it is
always artificial, I mean as in the case of wells, otherwise the
spring would have to be above the outlet. Hence the water from
fountains and rivers flows of itself, whereas wells need to be
worked artificially. All the waters that exist belong to one or
other of these classes.
On the basis of this division we can sec that the sea cannot have
springs. For it falls under neither of the two classes; it does not
flow and it is not artificial; whereas all water from springs must
belong to one or other of them. Natural standing water from springs is
never found on such a large scale.
Again, there are several seas that have no communication with one
another at all. The Red Sea, for instance, communicates but slightly
with the ocean outside the straits, and the Hyrcanian and Caspian seas
are distinct from this ocean and people dwell all round them. Hence,
if these seas had had any springs anywhere they must have been
discovered.
It is true that in straits, where the land on either side
contracts an open sea into a small space, the sea appears to flow. But
this is because it is swinging to and fro. In the open sea this
motion
is not observed, but where the land narrows and contracts the sea
the motion that was imperceptible in the open necessarily strikes
the attention.
The whole of the
Mediterranean does actually flow. The direction
of this flow is determined by the depth of the basins and by the
number of rivers.
Maeotis flows into
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.
2
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
lie. So we must clearly look for something analogous in the case of
water. But here we can find no such single mass, as in the case of the
other elements, except the sea. River water is not a unity, nor is
it stable, but is seen to be in a continuous process of becoming
from day to day. It was this difficulty which made people regard the
sea as the origin and source of moisture and of all water. And so we
find it maintained that rivers not only flow into the sea but
originate from it, the salt water becoming sweet by filtration.
But this view involves another difficulty. If this body of water
is the origin and source of all water, why is it salt and not sweet?
The reason for this, besides answering this question, will ensure
our having a right first conception of the nature of the sea.
The earth is surrounded by water, just as that is by the sphere of
air, and that again by the sphere called that of fire (which is the
outermost both on the common view and on ours). Now the sun, moving as
it does, sets up processes of change and becoming and decay, and by
its agency the finest and sweetest water is every day carried up and
is dissolved into
vapour and rises to the upper region, where it is
condensed again by the cold and so returns to the earth. This, as we
have said before, is the regular course of nature.
Hence all my predecessors who supposed that the sun was nourished by
moisture are absurdly mistaken. Some go on to say that the solstices
are due to this, the reason being that the same places cannot always
supply the sun with nourishment and that without it he must perish.
For the fire we are familiar with lives as long as it is fed, and
the only food for fire is moisture. As if the moisture that is
raised could reach the sun! or this ascent were really like that
performed by flame as it comes into being, and to which they
supposed the case of the sun to be analogous! Really there is no
similarity. A flame is a process of becoming, involving a constant
interchange of moist and dry. It cannot be said to be nourished
since it scarcely persists as one and the same for a moment. This
cannot be true of the sun; for if it were nourished like that, as they
say it is, we should obviously not only have a new sun every day, as
Heraclitus says, but a new sun every moment. Again, when the sun
causes the moisture to rise, this is like fire heating water. So, as
the fire is not fed by the water above it, it is absurd to suppose
that the sun feeds on that moisture, even if its heat made all the
water in the world evaporate. Again, it is absurd, considering the
number and size of the
stars, that these thinkers should consider
the sun only and overlook the question how the rest of the heavenly
bodies subsist. Again, they are met by the same difficulty as those
who say that at first the earth itself was moist and the world round
the earth was warmed by the sun, and so air was generated and the
whole firmament grew, and the air caused winds and solstices. The
objection is that we always plainly see the water that has been
carried up coming down again. Even if the same amount does not come
back in a year or in a given country, yet in a certain period all that
has been carried up is returned. This implies that the celestial
bodies do not feed on it, and that we cannot distinguish between
some air which preserves its character once it is generated and some
other which is generated but becomes water again and so perishes; on
the contrary, all the moisture alike is dissolved and all of it
condensed back into water.
The drinkable, sweet water, then, is light and is all of it drawn
up: the salt water is heavy and remains behind, but not in its natural
place. For this is a question which has been sufficiently discussed (I
mean about the natural place that water, like the other elements, must
in reason have), and the answer is this. The place which we see the
sea filling is not its natural place but that of water. It seems to
belong to the sea because the weight of the salt water makes it remain
there, while the sweet, drinkable water which is light is carried
up. The same thing happens in
animal bodies. Here, too, the food
when it enters the body is sweet, yet the
residuum and
dregs of liquid
food are found to be bitter and salt. This is because the sweet and
drinkable part of it has been drawn away by the natural animal heat
and has passed into the flesh and the other parts of the body
according to their several natures. Now just as here it would be wrong
for any one to refuse to call the belly the place of liquid food
because that disappears from it soon, and to call it the place of
the residuum because this is seen to remain, so in the case of our
present subject. This place, we say, is the place of water. Hence
all rivers and all the water that is generated flow into it: for water
flows into the deepest place, and the deepest part of the earth is
filled by the sea. Only all the light and sweet part of it is
quickly carried off by the sun, while herest remains for the reason we
have explained. It is quite natural that some people should have
been puzzled by the old question why such a mass of water leaves no
trace anywhere (for the sea does not increase though innumerable and
vast rivers are flowing into it every day.) But if one considers the
matter the solution is easy. The same amount of water does not take as
long to dry up when it is spread out as when it is gathered in a body,
and indeed the difference is so great that in the one case it might
persist the whole day long while in the other it might all disappear
in a moment-as for instance if one were to spread out a cup of water
over a large table. This is the case with the rivers: all the time
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.
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