by Aristotle
Since there is necessarily some change in the whole world, but not in the way of coming into existence or perishing (for the universe is permanent), it must be, as we say, that the same places are not for ever moist through the presence of sea and rivers, nor for ever dry. And the facts prove this. The whole land of the Egyptians, [20] whom we take to be the most ancient of men, has evidently come into existence and been produced by the river. This is clear from an observation of the country itself, and the facts about the Red Sea suffice to prove it too. One of their kings tried to [25] make a canal to it (for it would have been of no little advantage to them for the whole region to have become navigable; Sesostris is said to have been the first of the ancient kings to try), but he found that the sea was higher than the land. So he first, and Darius afterwards, stopped making the canal, lest the sea should mix with the [30] river water and spoil it. So it is clear that all this part was once one unbroken sea. For the same reason Libya—the country of Ammon—is, strangely enough, lower and hollower than the land to the seaward of it. For it is clear that a barrier of silt was formed and after it lakes and dry land, but in the course of time the water that was left behind in the lakes dried up and is now all gone. Again the silting up of the [353a1] lake Maeotis by the rivers has advanced so much that the limit to the size of the ships which can now sail into it to trade is much lower than it was sixty years ago. Hence it is easy to infer that it, too, like most lakes, was originally produced by the [5] rivers and that it must end by drying up entirely.
Again, this process of silting up causes a continuous current through the Bosporus; and in this case we can directly observe the nature of the process. Whenever the current from the Asiatic shore threw up a sandbank, there first formed a small lake behind it. Later it dried up and a second sandbank formed in [10] front of the first and a second lake. This process went on uniformly and without interruption. Now when this has been repeated often enough, in the course of time the strait must become like a river, and in the end the river itself must dry up.
So it is clear, since there will be no end to time and the world is eternal, that [15] neither the Tanais nor the Nile has always been flowing, but that the region whence they flow was once dry; for their action has an end, but time does not. And this will be equally true of all other rivers. But if rivers come into existence and perish and [20] the same parts of the earth were not always moist, the sea must needs change correspondingly. And if the sea is always advancing in one place and receding in another it is clear that the same parts of the whole earth are not always either sea or land, but that all this changes in the course of time.
So we have explained that the same parts of the earth are not always land or [25] sea and why that is so; and also why some rivers are perennial and others not.
BOOK II
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 concerned themselves with theogonies say that the sea has springs, for they want earth and sea to have origins and roots. Presumably they [353b1] 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 [5] 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 [10] sea is being dried up and is growing less, and will end by being some day entirely dried up. Some of them 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 [15] 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 have springs. The waters we find on the earth either flow or are stationary. All flowing water has [20] springs. (By a spring, as we have explained above, we must not understand a source from which waters are ladled16 as it were from a vessel, but a first point at which17 the water which is continually forming and percolating gathers.)18 Stationary water is either that which has collected and has been left standing, marshy pools, for [25] 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. For the spring must always be higher than the stream. 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 [30] or other of these classes.
On the basis of this division we can see 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 belongs to one or other of them. Natural standing water from springs is never found on such a large scale.
[354a1] 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 [5] 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 evidently flows. 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 [10] the sea the motion that was slight in the open necessarily seems great.
The whole of the Mediterranean does actually flow, according to the depth of the basins and the number of rivers. Maeotis flows into Pontus and Pontus into the [15] 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 areas many times their size), and to their own shallowness. For we find the sea getting deeper and deeper. Pontus is deeper than [20] Maeotis, the Aegean than Pontus, the Sicilian sea than the Aegean; the Sardinian and Tyrrhenic being the deepest of all. (Outside the pillars of Herakles 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 [25] 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 [30] 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 [354b1] cause of its salt and bitter taste.
What made earlier writers consider the sea to be the source and main body of all water is this. It seems reasonable to suppose that, just as each of the other [5] elements 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 [10] 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 source of moisture and of all water. And so we [15] find it maintained th
at 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 source of [20] 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 [25] 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 [30] 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, [355a1] 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. This supposes that the [5] moisture that is raised reaches the sun or that its ascent is 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 in a process of becoming, involving a constant interchange of moist and dry. It cannot be said to be nourished [10] 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, [15] 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 is, 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 [20] overlook the question how the rest of the heavenly bodies survive. 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 [25] the whole firmament grew, and the air caused winds and the solstices. For 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 fixed 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 [30] 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 proper place. For this is a question which has been sufficiently discussed (for it would be unreasonable if there were no [355b1] place for water as there is for the other elements), and the answer is this. The place which we see the sea filling is not its 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, [5] 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 [10] drinkable part of it has been drawn away by the natural 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 wrong19 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 [15] 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. But part of it is all quickly carried up by the sun, while the rest [20] 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. [25] 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 [30] compact mass, but when it arrives at a vast wide place it quickly and imperceptibly evaporates.
But the theory of the Phaedo20 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 [356a1] 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; for it has no fixed seat but is always oscillating about the centre. Its motion up [5] 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 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 [10] 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 [15] 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 [20] 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. Yet 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 [25] through a low-lying 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.21 All of which is plainly [30] 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, [356b1] 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 is always the same, or whether it did not exist at all once and some day will exist no longer, but [5] 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 [10] 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 th
e islands; and when she sucks it in for the last [15] 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 [20] 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 [25] must be 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;22 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 [30] whenever it approaches, and let it descend again when it recedes. This notion about the sea was 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 [357a1] earth will grow dry once again. We must recognize that this process always goes on thus in a cycle; for that is more reasonable 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.