Aristotle · a new plain-English translation from the original language
1| Meteorology, Book 1. We have already spoken of the first causes of nature and of all natural motion, and also of the stars ordered in the upward motion, and of the bodily elements — how many and what kind they are, and their change into one another — and of coming-to-be and passing-away in general. What remains is a further part of this inquiry still to be considered, the part which all our predecessors called meteorology. This concerns all that happens by nature, though with less order than belongs to the first of the bodies, and occurs mostly in the region bordering the motion of the stars — for example, the Milky Way, comets, and the fiery and moving apparitions, and whatever we should set down as affections common to air and water, and further the kinds, parts, and affections of the parts of earth, from which we may go on to consider the causes of winds and earthquakes and of everything that happens in virtue of their motions. On some of these we are at a loss, while on others we have some grasp. There remains also the fall of thunderbolts, and typhoons and fiery whirlwinds, and the other recurring phenomena, all the affections that happen to these same bodies through a process of solidification. Once we have gone through these matters, we will consider whether, following the method laid down, we are able to give some account of animals and plants, both in general and in their several kinds. For once these have been discussed, our whole original undertaking will be more or less complete. Let us begin, then, and speak of these matters first.
2| We have already determined that there is one principle of the bodies out of which the nature of the bodies moving in a circle is composed, and four other bodies owing to the four principles, whose motion we say is twofold, one away from the middle, the other toward the middle. These four are fire, air, water, and earth; and of these, fire is the one that rises above all the rest, and earth the one that settles beneath them all; two others stand in analogous relation to these — air is nearest of the rest to fire, water to earth. The whole world about the earth, then, is composed of these bodies, and it is the affections that occur in this world that we say must be grasped. This world is of necessity in some way continuous with the revolutions above, so that its whole power is governed from there; for that from which the principle of motion comes to all things must be reckoned the first cause. Further, the motion of that upper region is eternal and has no end in respect of place, but is always at its end, whereas these bodies here all stand apart from one another in bounded places. Hence, of the things that happen about this lower world, fire and earth and their kindred must be held to be causes in the manner of matter for the things that come to be — for it is in this sense that we speak of what underlies and is acted upon — while that which is a cause in the sense of being the source of the principle of motion must be attributed to the power of the bodies that are always in motion.
3| Taking up again, then, the positions laid down at the start and the distinctions already stated, let us speak of the appearance called the Milky Way, and of comets, and of whatever else happens to be akin to these. We say that fire, air, water, and earth come to be out of one another, and that each is present potentially in each of the others, just as with other things that have some one and the same underlying subject into which they are ultimately resolved. Now first of all one might raise a difficulty about what is called air: what nature must we take it to have within the world that surrounds the earth, and how is it ordered in relation to the other so-called elements of bodies? For how great a mass the earth is in comparison with the surrounding magnitudes is not unclear, since it has already been seen, through the theorems of astronomy, that it is much smaller even than some of the stars. But a nature of water that is constituted and marked off by itself we neither see, nor can it exist separated from the body settled about the earth — as with the visible waters, sea and rivers, and whatever at depth is unclear to us. But as for what lies between the earth and the outermost stars, must we suppose it to be one body in nature, or several? And if several, how many, and up to what point is it marked off by places?
4| We have already spoken of the first element, of what sort its power is, and that the whole world of the upward motions is full of that body. And this opinion is not one we alone happen to hold; it appears to be an ancient supposition, held also by men of former times. For the thing called aether has received this name from of old, a name which Anaxagoras, it seems to me, meant to be the same as fire — for he thought the upper regions full of fire, and supposed that the power there was what aether meant, and in this he thought rightly. For it seems men have supposed that whatever body is always in motion is in its nature something divine, and accordingly they marked it off by the name aether, as being the same as none of the things about us. For we shall not say that the same opinions recur among men once, or twice, or a few times, but infinitely many times. As for those who say that what surrounds us is pure fire, and not merely the bodies that are borne along in it, and that what lies between earth and the stars is air, had they considered what is now shown adequately through the mathematical sciences, they would perhaps have given up this childish opinion. For it is too simple to suppose, because each of the moving bodies appears small to us looking at them from here, that it is therefore small in magnitude.
5| Now this has already been said before, in the discussions on the upper region, but let us state the same argument again now. For if the intervening spaces were full of fire, and the bodies were composed out of fire, each of the other elements would long ago have vanished. But neither, on the other hand, are they full of air alone; for it would far exceed the equality of the common proportion in relation to the bodies of its own rank — and this even if the region between earth and heaven were full of two elements. For the mass of the earth is virtually no part, so to speak, of the surrounding magnitude, even when the whole quantity of water is taken along with it. But we do not observe so great an excess of bulk occurring when air comes to be out of water separated out, or fire out of air. And the ratio that a given small quantity of water bears to the air that comes to be from it must necessarily be the same ratio that the whole of air bears to the whole of water. And it makes no difference even if someone should say that these do not come to be out of one another, but merely have equal power; for in this way too the equality of power must hold for their magnitudes, just as it would if they did come to be out of one another.
6| That, then, neither air nor fire alone has filled up the intervening region is clear. It remains, having gone through the difficulty, to say how the two are ordered in relation to the position of the first body — I mean air and fire — and for what cause the heat from the stars above reaches the regions about the earth. Having spoken first of air, as we proposed, let us in the same way speak again of these matters. If, then, water comes to be out of air and air out of water, for what cause do clouds not form in the upper region? For it would be more fitting the farther off and colder the region is, since it is neither so near the stars, which are hot, nor near the rays reflected from the earth, which prevent condensation from forming near the earth by separating out the condensations through their heat — for the gathering together of clouds occurs where the rays already come to an end, being scattered into the boundless. Either, then, water is not naturally formed out of all air alike, or, if it is formed alike out of all, the region about the earth is not air alone but something like vapor, and this is why it condenses again into water.
7| But surely, if the air, vast as it is, were entirely vapor, the nature of air would seem to far exceed that of water — given that the intervening spaces above are full of some body, and it cannot be fire (since everything else would then have been dried up), so what remains is air, and water surrounding the whole earth; for vapor is a separating-off of water. Let this be the difficulty raised about these matters in this way; but let us now speak, drawing distinctions both with a view to what will be said and with a view to what has just been stated. For we say that the region above, up to the moon, is a body distinct from both fire and air; nevertheless, within it itself, one part is purer and another less unmixed, and it has differences, especially where it terminates toward the air and toward the world around the earth. As the first element and the bodies within it are carried around in a circle, the part of the lower world and body always nearest to it, being separated out by the motion, is kindled into fire and produces heat. We must conceive the matter this way, starting from the following point. The body beneath the upper revolution, being as it were a kind of matter, and potentially hot and cold and dry and wet, and whatever other affections follow upon these, becomes actually such and is such through motion and rest, the cause and principle of which we stated earlier.
8| At the center, then, and around the center, what is heaviest and coldest has been separated off — earth and water; and around these, and next to them, air, and what we call, by custom, fire, though it is not fire; for fire is an excess of heat and a kind of boiling. But we must understand that, of what we call air, the part around the earth is, so to speak, moist and hot, because it contains vapor and holds the exhalation of the earth, while the part above this is by now hot and dry. For the nature of vapor is moist and hot, and that of exhalation is hot and dry; and vapor is potentially, as it were, water, while exhalation is potentially, as it were, fire. This, then, must be supposed to be the reason why clouds do not form in the upper region: that it does not contain air alone, but rather something more like fire. Nothing prevents the circular motion, too, from also being a reason why clouds are hindered from forming in the upper region; for all the air that revolves in a circle must necessarily flow — as much of it, that is, as is not taken up within the circumference that completes the earth's being wholly spherical. For even now the generation of winds is evidently found in the low-lying, stagnant regions of the earth, and the winds are seen not to rise above the highest mountains.
9| It flows in a circle because it is dragged along by the revolution of the whole. For fire is continuous with the upper element, and air is continuous with fire; so that, on account of this motion too, it is prevented from condensing into water, but instead, whatever part of it becomes heavy is always carried downward, while the hot is squeezed out into the upper region, and other parts in turn are carried up together with the fire that rises as exhalation; and in this way one region continuously remains full of air and another full of fire, and each of them is always becoming different from what it was. About why clouds do not form, and there is no condensation into water, and about how we should understand the region between the stars and the earth, and what body it is full of, let this much be said. As for the heat that comes to be, which the sun supplies, it is more proper to speak of it precisely and in its own right in the works on perception (for the hot is a certain affection of perception); but for what cause it comes about, given that those upper bodies are not of that nature, must be stated here too. We observe, then, that motion is able to separate out the air and set it ablaze, so that things carried through it are often seen to melt. So then, the sun's motion by itself is sufficient to produce the warmth and heat that arise —
10| for it must be both swift and not far off. Now the motion of the stars is swift but far off, and that of the moon is near but slow; but the sun's motion has both of these sufficiently. That the heat comes to be especially together with the sun itself is reasonable, if we take the parallel from what happens among us; for here too, of things carried by force, the air nearest to them becomes hottest. And this happens reasonably enough; for it is above all the motion of the solid body that separates it out. For this reason, then, heat reaches this region of ours, and also because the fire surrounding the air is often scattered by the motion and carried down by force. A sufficient sign that the upper region is neither hot nor set ablaze is also the shooting of the stars. For these do not occur there, but lower down; and yet things that move more are kindled more. Besides this, the sun, which seems to be hottest of all, appears white, not fiery in color.
11| Now that these matters have been determined, let us say for what cause burning flames appear in the sky, and shooting stars, and what some call torches and goats; for all these are the same thing and occur through the same cause, differing only in degree. The starting point for these, and for many other things, is the following. For when the earth is heated by the sun, the exhalation that necessarily arises is not single, as some suppose, but double: one more vaporous, the other more windy — the one being the vapor of the moisture in and on the earth, the other a smoky exhalation of the earth itself, which is dry. And of these, the windy exhalation rises to the surface because of its heat, while the moister one settles below because of its weight. And because of this the surrounding region is ordered in the following way: first, immediately beneath the circular motion, is the hot and dry, which we call fire (for there is no name common to the whole of this smoky separation; nevertheless, because such a body is by nature especially disposed to catch fire, we are forced to use these names in this way), and beneath this nature comes air. We must understand that this fire we have just spoken of is stretched around, like fuel, at the outermost part of the sphere surrounding the earth, so that, meeting with only a slight motion, it often catches fire, just like smoke —
12| for flame is the boiling of dry wind. So wherever this kind of composition happens to be most favorably disposed, it catches fire whenever it is somehow set in motion by the revolution. And it differs, from this point on, according to the position or the quantity of the fuel. For if the fuel has both breadth and length, a burning flame is often seen, like stubble burning in a field; but if it has length only, the result is what are called torches and goats and shooting stars. And if the fuel is greater in length than in breadth, then, when it as it were throws off sparks as it burns (this happens because it catches fire further along at the edges, in small amounts, but continuously from the start), it is called a goat; but when it burns without this effect, it is called a torch. But if the lengths of the exhalation are scattered in small portions and in many places, and likewise in breadth and depth, the result is what appear to be shooting stars. So sometimes it is the exhalation, catching fire because of the motion, that produces them; but sometimes the hot is struck out and squeezed out by the air that condenses on account of cooling, which is why their movement resembles a hurling rather than a burning. For one might raise the question whether, just as the vapor placed beneath lamps is ignited by the flame above and lights the lamp below (for the speed of this too is remarkable, and resembles a hurling rather than one fire after another coming to be), so also shooting stars are the hurling of one and the same body.
13| It seems, then, that it comes about through both causes: partly in the way that light comes from a lamp, and partly because some of these bodies are shot out by being squeezed, like the seeds squeezed out from between the fingers, so that they appear to fall both into the sea and onto the land, both at night and by day when the sky is clear. They are shot downward because the condensation that pushes them out inclines downward. This is also why thunderbolts fall downward: for the origin of all these things is not a burning up but a separating out caused by compression, since by nature everything hot naturally tends to travel upward. So whatever forms in the very highest region comes about by the exhalation being set on fire, while whatever forms lower down comes about by separation, because the moister exhalation condenses and cools; for this exhalation, condensing and inclining downward, pushes the hot substance out as it grows denser, and makes its ejection go downward. But because of the position of the exhalation, wherever it happens to lie in breadth and in depth, the hot substance is carried either upward or downward or sideways. Most of the time it goes sideways, because two motions are at work on it: by force, downward, and by nature, upward; for all such bodies travel along the diagonal of these two.
14| This is also why the greatest part of the motion of shooting stars turns out to be slanting. The cause of all these things, as matter, is the exhalation, while as the moving cause it is sometimes the upward motion, sometimes the solidifying of the air as it is compressed together. All these phenomena occur below the moon. A sign of this is that their apparent speed is like that of things thrown by us, which, because they are close to us, seem by their speed to far outstrip the stars, the sun, and the moon.
15| Sometimes many appearances are seen forming in the sky at night when the sky is clear, such as chasms and pits and blood-colored patches. The cause of these too is the same. For since it is evident that the upper air condenses to the point of catching fire, and that this catching fire sometimes happens in such a way that it looks like a burning flame, and sometimes like firebrands and stars being carried along, it is not strange if this same air, as it condenses, takes on colors of every kind; for the air, being seen through as denser and admitting less light, and also receiving reflection, will produce colors of every kind, but especially crimson or purple, because these colors most of all appear when fiery and white are mixed together as bodies come in front of one another—just as stars, when they are rising and setting, appear crimson if there is a heat-haze, and appear crimson when seen through smoke. And it will produce color by reflection too, whenever the mirroring surface is such that it receives not the shape but the color. The reason these appearances do not last long is that the condensation causing them is quick. The chasms come about when the light breaks apart out of a dark-blue and black background, making it seem to have some depth. Often firebrands fall out of such formations, when the material is compressed further together; and as something condenses it looks like a chasm. In general, white set within black produces many variegated effects, just as flame does within smoke. By day the sun prevents these appearances, and by night, apart from the crimson, the other colors do not show because of the sameness of color with the surrounding dark. Concerning shooting stars and bodies catching fire, and further concerning the other such appearances that produce their images swiftly, these are the causes one must suppose.
16| Let us now speak about comets and about what is called the Milky Way, first working through the difficulties raised by what others have said. Anaxagoras and Democritus, then, say that comets are a joint appearance of the wandering stars, occurring when they seem to touch one another because they have come close together. Some of the Italians, the so-called Pythagoreans, say that the comet is one of the wandering stars, but that its appearance occurs only after a long interval of time and its rising above the horizon is slight, which is also what happens with the star of Hermes; for because it rises only a little, it misses being seen on many occasions, so that it appears only after a long time. Hippocrates of Chios and his pupil Aeschylus declared much the same as these. Except that they say it does not have its hair from itself, but that the wandering star sometimes takes it on, depending on its position, when our sight is reflected from the moisture that is drawn up by it toward the sun. And because it falls behind very slowly in time, it appears only after a very long time compared to the other stars, as when it appears from the same point again, having fallen behind through its whole circle; and it falls behind both toward the north and toward the south. Now in the region between the tropics it does not draw the water to itself, because that region has been burned dry by the sun's course;
17| but when it travels toward the south, it has an abundance of such moisture, but because the segment of the circle above the earth is small, and the part below is many times larger, the sight of human beings cannot travel, being bent, all the way to the sun, since the star is neither near the tropic nor is the sun at the summer solstice. This is why in these regions the comet does not even occur; but whenever it happens to fall behind toward the north, it takes on hair, because the arc above the horizon is large there, and the part of the circle below is small; for then the sight of human beings easily reaches all the way to the sun. Now for all these thinkers, some things they say turn out to be impossible in common, and some individually. First, then, against those who say that the comet is one of the wandering stars: all the wandering stars fall behind within the circle of the zodiac, but many comets have been observed outside that circle. Further, more than one comet has often occurred at the same time. Besides this, if they have their hair through reflection, as Aeschylus and Hippocrates say, then this star ought at some time to appear without hair too, since it falls behind into other regions as well, but it does not have hair everywhere.
18| As it is, however, none has been observed apart from the five planets. And these are often seen all together, high above the horizon. And even when all of them are visible, and also when not all are visible but some are near the sun, comets are nonetheless seen occurring quite often. But indeed this is not true either, that a comet occurs only in the northern region, at the same time that the sun is around the summer solstice: for the great comet that occurred at the time of the earthquake in Achaea and the onrush of the wave rose from the direction of the equinoctial setting, and many comets have by now occurred toward the south as well. And when Euclees son of Molon was archon at Athens, a comet star occurred toward the north in the month Gamelion, when the sun was around the winter solstice; and yet they themselves say that so great a bending of the sight is among the impossibilities. Common to these thinkers and to those who speak of a joining together is, first, that some even of the fixed stars take on hair. And this we need not believe only on the authority of the Egyptians, although they too say it, but we ourselves have observed it; for one of the stars in the hip of the Dog had hair, faint indeed; for when people stared straight at it, its light became dim, but when they looked at it more gently out of the corner of the eye, more of it appeared.
19| Besides this, all the stars we have observed vanish without setting, fading away little by little in the region above the horizon, so that no body of a single star, or of several, is left behind. This happened even with the great star we mentioned earlier: it appeared in winter, in a spell of frost and clear skies, in the evening, in the archonship of Asteius. On the first day it was not seen, as it had already set before the sun, but on the following day it was seen; for as little as possible of it was left, and it set at once. Its light stretched out over a third of the sky, like a leap, which is why it was called "the Road." It extended as far as the belt of Orion, and there it dissolved. And yet Democritus has argued vigorously for his own view; for he says that when comets dissolve, certain stars have been seen. But this is not something that ought to happen sometimes and not others—it should happen always. Besides this, the Egyptians too say that conjunctions occur among the planets, both with one another and with the fixed stars, and we ourselves have twice already seen the star of Zeus come together with one of the stars in the Twins and make it disappear, without becoming a comet. And further, this is also plain from reasoning.
20| For the stars, whether they appear larger or smaller, nonetheless seem to be undivided in themselves. Just as, then, if they were actually undivided, their touching would not produce any greater magnitude, so too, since they are not undivided but only appear so, even when they come together they will appear no greater in magnitude than they are. That the explanations commonly given about them happen to be false is, then, sufficiently clear from these considerations, if not from a greater number.
21| Since we think we have given a sufficient account, so far as is possible, of things not accessible to perception, by reasoning them back as far as we can, one might suppose from what now appears that the following is roughly what happens concerning them. We take as established that of the world around the earth, so much of it as lies beneath the circular motion, the first part is a dry and hot exhalation. This exhalation, together with the air continuous with it beneath it, is carried around the earth to a great extent by the circular motion and revolution above; and being carried and moved in this way, wherever it happens to be in a well-tempered state, it often catches fire, which is why we say the shooting of the scattered stars occurs. So whenever a fiery beginning falls, on account of the motion of the bodies above, into such a condensation—one neither so great as to burn quickly and over a great extent, nor so weak as to be extinguished quickly, but more abundant and lasting—and at the same time a well-tempered exhalation happens to be rising up from below, this becomes a comet star, taking whatever shape the rising exhalation happens to have: if it is shaped alike on every side, it is a comet, but if it is drawn out in length, it is called a bearded star. And just as such a motion seems to be the motion of a star, so too a similar remaining-in-place seems to be the remaining-in-place of a star.
22| For what happens is much like what would happen if someone thrust a firebrand, or threw in some small beginning of fire, into a heap and quantity of chaff; for the shooting of the stars appears similar to this—because of the natural suitability of the fuel it spreads out quickly over a length. If, then, this were to persist and not fade away as it passes through, at the point where it most condensed the fuel, the end of the shooting would become the beginning of the further motion. A comet is a star of this kind, being like the shooting of a star, having within itself both an end and a beginning. So whenever the beginning of the formation is in the lower region itself, the comet appears on its own; but whenever the exhalation is formed by the motion of one of the heavenly bodies—either a fixed star or a planet—then one of these becomes a comet. For the hair does not form right at the stars themselves, but just as haloes appear around the sun and moon, following them even though the stars shift position, whenever the air is so condensed that this affection occurs along the sun's path, so too the hair is to the stars like a halo. Except that the halo gets its color in this way through reflection, whereas there the color is apparent in the bodies themselves.
23| So whenever such a combination occurs at a star, the comet must appear to move with the very same motion by which the star is carried; but whenever it forms on its own, then comets appear to lag behind. For such is the motion of the world around the earth. This especially indicates that the comet is not some kind of reflection, as a halo forming in pure fuel-material around the star itself, and not, as the followers of Hippocrates say, around the sun—because a comet often forms on its own, and more often than in connection with any of the fixed stars. About the halo we will state the cause later; but about their being composed of fire, one should take as evidence that most comets, when they occur, are signs of winds and droughts. For it is clear that they occur because such a discharge is great, so that the air must become drier, and the moisture that is being vaporized is separated out and dissolved by the abundance of the hot exhalation, so that it does not readily condense into water. We will speak more clearly about this affection too, when it is the right time to speak about winds. So whenever comets appear dense and numerous, as we say, the years become markedly dry and windy.
24| But when they are rarer and dimmer in magnitude, such a thing does not occur in the same way—though for the most part some excess of wind does occur, either in duration or in magnitude, since even when the stone fell from the air at Aegospotami, it was lifted up by wind and fell in daytime; and it happened that at that time too a comet star had appeared, in the evening. And around the time of the great comet star, the winter was dry and northerly, and the wave-surge occurred because of a clash of winds; for in the gulf the north wind held, while outside a great south wind was blowing. Further, in the archonship of Nicomachus at Athens, a comet appeared for a few days near the equinoctial circle, not making its rising in the evening, and it happened that the wind at Corinth occurred at that same time. The reason there are not many comets, nor frequent ones, and more of them outside the tropics than within them, is the motion of the sun and of the stars, which not only separates out the hot element but also disperses what is being formed. But the chief cause is that most of it collects in the region of the Milky Way.
25| Let us now say how and for what cause it occurs, and what the Milky Way is. Let us first go over what has been said about it by others as well. Some of those called Pythagoreans say that this is the path of one of the stars that fell, in the destruction spoken of in connection with Phaethon; others say that the sun once traveled on this circle, so that this region was, as it were, scorched, or suffered some other such affection because of its passage. But it is absurd not to notice that, if this were the cause, the circle of the zodiac ought to be affected in this way too, and more than the Milky Way; for all the planets travel in it, not the sun alone. And the whole circle is visible to us, for a visible semicircle of it is always present at night. But it appears to have suffered nothing of this kind, except where some part of it joins onto the circle of the Milky Way. Anaxagoras and Democritus and their followers say that the Milky Way is the light of certain stars; for they say that the sun, traveling beneath the earth, does not see some of the stars. Now the light of those stars overlooked by it is not visible (for it is blocked by the rays of the sun).
26| Those who are screened by the earth so that they are not seen by the sun—for these, they say, the Milky Way is their own proper light. It is clear that this too is impossible. For the Milky Way is always the same in relation to the same stars (for it appears to be the greatest circle), but the stars not seen because of the sun are always different ones, because the sun does not remain in the same place. It would have been necessary, then, as the sun shifted, for the Milky Way to shift as well; but in fact this is not seen to happen. Besides this, if things stand as shown in the theorems of astronomy—both that the sun's size is greater than the earth's, and that the distance of the stars from the earth is many times greater than the sun's distance from the earth, just as the sun's distance from the earth is greater than the moon's—then the cone cast from the sun would not bring its rays to a point anywhere near the earth, nor would the earth's shadow, called night, reach as far as the stars. Rather, the sun must necessarily look clean over all the stars, and the earth must screen none of them from it. There is, further, a third opinion held about this.
27| For some say that the Milky Way is a reflection of our sight toward the sun, just as they say of the star called the comet. This too is impossible. For if the one seeing, and the mirror, and the whole object seen were all at rest, the same part of the image would appear at the same point of the mirror; but if the mirror and the object seen were moving, at the same distance from the one seeing, who remains at rest, but not at equal speed relative to each other, nor always at the same interval from each other, it is impossible for the same image to remain at the same part of the mirror. Now the stars carried around in the circle of the Milky Way are in motion, and so is the sun, toward which the reflection is supposed to occur, while we ourselves remain at rest, and they are equally and equally far off from us, but not equally far off from one another; for sometimes the Dolphin rises at midnight, sometimes at dawn, while the same parts of the Milky Way remain fixed in each case. And yet this ought not to happen, if it were a reflected image, unless this affection belonged to those very places themselves. Further, at night, in water and mirrors of that kind, the Milky Way is seen to appear to those who look—but how is it possible for their sight to be reflected toward the sun then?
28| That the Milky Way, then, is neither the path of any of the planets, nor the light of stars not seen, nor a reflection, is clear from these arguments. These are more or less the accounts handed down up to now by others. Let us now state our own view, taking up again the principle laid down for us. For it has been said earlier that the outermost part of what is called air has the power of fire, so that when the air is separated out by motion, there is secreted such a composition as we say the comet stars also are. One must conceive that what happens here is of the same kind as what happens in those cases, when such a separating-out does not occur by itself, but is caused by one of the stars, either the fixed ones or the wandering ones; for then these appear as comets, because such a combination follows upon their motion, just as it follows upon the sun's, from which, on account of reflection, we say the halo appears, whenever the air happens to be mixed in that way. What happens, then, in the case of a single star must be taken to happen concerning the whole heaven and the whole upward motion together; for it stands to reason that, if the motion of one star does this, the motion of all of them together should produce something of the same kind and fan it up. And besides this, this should happen in that region where the stars happen to be most crowded, and most numerous, and largest.
29| Now the circle of the zodiac, because of the motion of the sun and of the planets, breaks up such a composition, which is why most comets occur outside the tropics. Further, a comet's tail occurs neither around the sun nor around the moon; for they disperse the exhalation too quickly for such a combination to form. But this circle, in which the Milky Way appears to those who look, happens to be both the greatest circle and one so positioned that it extends far beyond the tropics. Besides this, the region of the stars there is full both of the largest and brightest stars, and further of those called the scattered stars (this is plain to see even with the eyes), so that on account of all this, this whole combination is continuously and always being collected there. Here is a sign of it: even within the circle itself, the light is greater in the one semicircle that has the fold; for in this semicircle there are more and denser stars than in the other, which shows that the brightness comes to be for no other cause than the motion of the stars. For if it occurs both within this circle, in which most of the stars lie, and, within the circle itself, in that part where the stars appear to be more densely packed, both in size and in number, it is reasonable to suppose that this is the most proper cause of the phenomenon.
30| Let the circle and the stars in it be studied from the diagram. As for the so-called scattered stars, it is not possible to arrange them into the sphere in this way, because none of them has a clearly fixed position all the way through; but to those who look up into the sky it is evident, for only in this circle, of all the circles, are the spaces between the stars filled with such stars, while in the others there are plainly gaps. So if we accept the cause stated for the appearance of comets as reasonably given, we must suppose the Milky Way to be in the same condition; for what there, in a single star, is the affection called a tail, this same thing is found to occur, in the same way, around a whole circle, and the Milky Way is, so to speak, marked out as it were—the tail, due to the separating-out, of the greatest circle. This is why, as we said before, comets are neither many nor frequent, because such a composition is continuously being separated out and continues to be separated out, at each revolution, always into this same region. We have spoken, then, about the things that occur in the region of the world continuous with the motions around the earth—about the running of stars and the blazing flame, and further about comets and the so-called Milky Way.
31| For these are more or less all the phenomena that appear concerning this region. Let us now speak about the region that is second in position after this one, but first around the earth; for this is the region common to water and to air, and to what occurs in their upward generation. Here too we must grasp the principles and causes of everything alike. Now the one that moves things, and rules, and is first among the principles, is the circle in which the sun's motion plainly, by separating and combining through coming nearer or farther off, is the cause of generation and destruction. While the earth remains at rest, the moisture around it, turned to vapor by the sun's rays and by the other heat from above, is carried upward; but when the heat that carries it up fails—part of it being dispersed into the upper region, part being quenched because it rises too far into the air above the earth—the vapor condenses again as it cools, both because the heat has failed it and because of the place it has reached, and it becomes water out of air; and once it has become water, it is carried back again toward the earth. Now the exhalation from water is vapor, and the exhalation from air into water is cloud.
32| Mist is a residue left over from the condensation of cloud into water. That is precisely why it is more a sign of fair weather than of rain: mist is, so to speak, a barren cloud. This cycle occurs in imitation of the sun's cycle: for as the sun shifts sideways, this too shifts up and down. And one must think of it as a river flowing in a circle, up and down, shared between air and water: when the sun is near, the river of vapor flows upward; when the sun withdraws, the river of water flows downward. And this tends to happen continuously, at least as a regular order, so that if the ancients were hinting at this in speaking of Ocean, they would perhaps mean this very river, the one that flows in a circle around the earth. Since the moisture is always being drawn up because of the power of heat, and again carried back down toward the earth because of cooling, names have been assigned appropriately to these processes and to certain differences among them: when it is carried down in small portions, it is called drizzle; when in larger portions, it is called rain.
33| Of the moisture that evaporates daily, whatever is not lifted high because the fire that draws it up is too weak relative to the water being drawn up, and is carried back down again when it is cooled at night, is called dew or frost. It is frost when the vapor freezes before it has condensed again into water (this happens in winter, and more in wintry regions); it is dew when the vapor has condensed into water, and the warmth is not so great as to dry up what has been drawn up, nor the cold so great as to freeze the vapor itself, because the place is warmer or the season is milder. For dew occurs more in fair weather and in the milder regions, while frost, as has been said, occurs in the opposite conditions; for it is clear that vapor is warmer than water, since it still retains the fire that draws it up, so that a greater degree of cold is needed to freeze it. Both occur in clear, windless weather: neither will be drawn up without a clear sky, nor could it condense while wind is blowing. A sign that these arise because the vapor is not lifted far is that frost does not occur on mountains. One cause is this: the vapor is drawn up from hollow, well-watered places, so that the heat drawing it up, carrying more than it can bear on its own, is unable to lift it very high, but lets it go again close by;
34| a second cause is that the air, which flows most strongly at high altitudes, dissolves such a condensation there. Dew occurs everywhere with south winds, not north winds, except in the region of the Black Sea; there it is the opposite, for it occurs with north winds and not with south winds. The cause is similar to the reason dew occurs in fair weather and not in storms: the south wind produces fair weather, the north wind produces storms, since it is cold, and so it quenches the heat of the rising vapor because of its wintry character. But in the region of the Black Sea the south wind does not produce fair weather to the degree needed for vapor to form, while the north wind, by its coldness, forces the heat back on itself and gathers it together, so that more vapor rises. This can often be seen happening in other places as well: wells give off more vapor with north winds than with south winds. But north winds quench the vapor before any quantity of it can gather, whereas with south winds the rising vapor is allowed to accumulate. The water itself does not freeze there, as it does in the region where clouds form.
35| From that region three bodies come down, formed by the cold: water, snow, and hail. Two of these occur analogously and for the same causes as the phenomena below, differing only in degree and in quantity; for snow and frost are the same thing, and so are rain and dew, except that one is abundant and the other slight. Rain comes from a great quantity of vapor being cooled; the cause of this is that the region from which it is gathered, and the time over which it is gathered, are both extensive. Dew is the slight case: its formation is a matter of a single day, and its region is small; this is shown by the fact that its generation is quick and its quantity slight. Frost and snow are alike in the same way: when the cloud freezes, it is snow; when the vapor freezes, it is frost. Hence frost is a sign of a cold season or a cold region, for it would not freeze while there was still much heat present, unless the cold was overpowering it. For in the cloud there is still much of the heat left over from the fire that evaporated the moisture out of the earth. Hail occurs up there, but is lacking in the vapor that rises near the earth; for, as we said, what is snow up there becomes frost down here, and what is rain up there becomes dew down here; but what is hail up there does not have any corresponding counterpart down here. The cause of this will become clear once we have spoken about hail.
36| One must at the same time take in the facts observed about hail's generation, both those that raise no difficulty and those that seem paradoxical. Hail is ice, and water freezes in winter; yet hailstorms occur mostly in spring and autumn, then also in late summer, and rarely in winter, and when they do, it is when the cold is less severe. And in general hail occurs in the milder regions, snow in the colder ones. It is also strange that water should freeze in the upper region at all: for it cannot freeze before it has become water, and water cannot remain suspended aloft for any length of time. And yet it is not the case, as with drizzle, which is carried aloft because of its smallness and lingers in the air (just as on water, earth and gold often float because their particles are small) — it is not the case that water similarly stays up in the air, with many small particles then coming together and falling down as large drops of drizzle; for this cannot happen with hail, since frozen bodies do not fuse together the way liquids do. It is clear, then, that so much water remained up there, for otherwise so much could not have frozen. Some hold that the cause of this affection and of its generation is that the cloud is pushed up into the upper region, which is colder because the reflections of the sun's rays from the earth cease there, and that once it arrives there the water freezes.
37| That is also why, they say, hail occurs more in summer and in warm regions: because the heat pushes the clouds up further from the earth. But it turns out that hail occurs least of all in very high places, though on this account it ought to occur most there, just as we observe that snow occurs most on high ground. Moreover, clouds have often been seen moving with a great noise close to the very ground itself, so that it is frightening to those who hear and see it, as though something greater were about to happen; and sometimes, when such clouds have been seen even without noise, a great deal of hail falls, incredible in size, and not round in shape, because its fall does not take long, given that its freezing happened close to the earth — not as those others claim. But in fact it is necessary, by the very cause most responsible for freezing, that large hailstones be produced; for hail is ice, and this is plain to everyone. The large hailstones are the ones not round in shape. This is a sign that the freezing happened close to the earth; for stones carried from far away, because they travel a long distance, get worn round by collision and end up rounder in shape and smaller in size. It is clear, then, that the freezing does not happen because the cold pushes the cloud up into the upper region.
38| But since we observe that a mutual displacement occurs between the hot and the cold — which is why, in hot weather, the regions below the earth are cold, and in frosts they are warm — we must think that this happens in the upper region too, so that in the warmer seasons the cold, being displaced inward by the heat surrounding it, sometimes quickly makes water out of the cloud, sometimes hail. That is why raindrops become much larger on warm days than in winter, and the rains more violent; for rains are called violent when they fall more concentrated, and concentrated because of the speed of the condensation. This happens in exactly the opposite way to what Anaxagoras says: he says this happens when the cloud returns up into the cold air, but we say it happens when it comes down into the hot air, and most of all when this is most the case. And when the cold is displaced still further inward by the heat outside, having made water it then freezes it, and hail results. This occurs whenever the freezing is faster than the downward motion of the water; for if the water is carried down in such-and-such a time, and the cold, being intense, freezes it in less time than that, nothing prevents it from freezing while still up in the air, provided the freezing takes less time than the downward journey.
39| And the nearer to the ground and the more concentrated the freezing occurs, the more violent the rains become, and the raindrops and hailstones larger, because they travel only a short distance. And for the same reason the large raindrops do not fall thickly. This happens less in summer than in spring and autumn, but more than in winter, because the air is drier in summer; in spring it is still moist, and in autumn it is already growing moist. Hail sometimes occurs even at harvest-time, as has been said, for the same cause. What also contributes to the speed of the freezing is that the water has been heated beforehand, for it cools faster. That is why many people, when they want to cool water quickly, first put it in the sun; and the people around the Black Sea, when they pitch their tents on the ice for fishing (for they hunt by cutting through the ice), pour hot water around their reed poles because it freezes faster — they use the ice as they would lead, so that the reeds stay fixed and still. Water that is condensing quickly becomes warm, both in warm regions and in warm seasons. And in the region of Arabia and Ethiopia the rains occur in summer and not in winter, and these are torrential, and often several times in the same day, for the same cause —
40| for it cools quickly through the mutual displacement, which occurs because the region is intensely hot. Concerning rain, dew, snow, frost, and hail, then — the cause for which they occur and what their nature is — let this much be said.
41| Concerning winds and all currents of air, and further concerning rivers and the sea, let us speak — first raising, for ourselves, difficulties about these matters too; for just as with other subjects, so too concerning these we have received nothing said that even any chance person might not have said. There are some who say that what is called air, when moving and flowing, is wind, and this same thing, when it condenses, is again cloud and water, on the ground that water and wind are of the same nature, and that wind is a motion of air. That is why, among those who wish to speak with wisdom, some say that all the winds are one wind, because it turns out that the air in motion is one and the same throughout, and it only seems to differ — though it does not differ at all — because of the places from which it happens to flow on each occasion; they speak in much the same way as someone would who thought that all rivers were one river. That is why the many, speaking without inquiry, speak better than those who speak this way with inquiry. For if all winds flowed from one source, and the currents of air behaved in the same way there too, then perhaps those who speak this way would be saying something; but if it is the same here and there, clearly this clever claim would be false, since the matter deserves a proper examination in its own right: what wind is, and how it comes about, and what moves it, and where its origin comes from, and whether one must suppose that wind flows out as from a vessel, and continues flowing until the vessel is emptied, as though released from wineskins, or rather, as painters also depict it, as figures releasing the source of the wind from within themselves.
42| Similarly, some think it is with the coming-to-be of rivers too: the water drawn up by the sun, raining down again, collects under the earth and flows out from a great cavity — either all rivers from one cavity, or different rivers from different ones — and no water comes to be at all, but the multitude of the rivers is simply what has been collected from the winter rains into such receptacles. That is why, they say, rivers always flow fuller in winter than in summer, and some are perennial while others are not: for those whose cavity is so large that the water collected in it is abundant, so that it lasts and is not used up before the winter rain comes round again to replenish it, these flow perennially throughout; but those whose receptacles are smaller, these, because of the scantiness of their water, dry up before what comes from the sky arrives, since the vessel has been emptied. And yet it is obvious, if one is willing to construct, as it were, a receptacle before one's eyes for the water that flows continuously day after day, and to grasp its quantity in thought, that it would exceed the mass of the earth in size, or would fall not far short of receiving all the water that flows in the course of a year.
43| But it is clear that many such things do happen in many places on the earth; nonetheless it is absurd if someone should fail to think that water comes to be from air for the same cause both above the earth and within it. So that if there too, through cold, the vaporizing air condenses into water, one must think this same thing happens because of the cold within the earth as well, and that not only does the water already separated out within it come to be and then flow, but that it comes to be continuously. Further, that the source of rivers, for water that is not coming-to-be but already exists day by day, is not of the sort some describe — certain lakes separated off under the earth, as some say — but rather, just as in the region above the earth small drops form and gather, and again these gather into others, until finally the rainwater comes down in quantity, so also in the earth it first trickles together out of small amounts, and it is as though the earth, sweating into one place, forms the sources of rivers. The very facts show this: for those who construct water-conduits gather the water by tunnels and channels, as though the earth were sweating down from the high places. That is why the streams of rivers evidently flow from mountains, and the most numerous and greatest rivers flow from the greatest mountains.
44| Similarly, most springs too lie close to mountains and high places; but on plains, apart from rivers, very few occur at all. For mountainous and elevated regions, like a dense sponge hanging overhead, seep and trickle water together little by little but in many places; for they receive a great quantity of the water descending onto them (for what difference does it make whether the curved surface is hollow and facing up, or projecting and convex? In both cases it will enclose an equal bulk of matter), and they cool the rising vapor and combine it again into water. That is why, as we said, the greatest of the rivers evidently flow from the greatest mountains. This is clear to those who study surveys of the earth; for these have been written down from inquiring of each people in this way, for those places which the writers themselves did not happen to see with their own eyes. In Asia, then, the most numerous and the greatest rivers evidently flow from the mountain called Parnassus, and this is agreed to be the greatest of all mountains toward the winter sunrise; for to one who has crossed it, the outer sea already comes into view, whose limit is not clear to people from here. From this mountain, then, flow other rivers as well as the Bactrus and the Choaspes and the Araxes —
45| A branch of this splits off as the Tanaïs, flowing into Lake Maeotis. The Indus too flows from it — the greatest flow of all rivers. From the Caucasus flow many other rivers as well, surpassing others in both number and size, including the Phasis. The Caucasus is the greatest mountain of those toward the summer sunrise, both in extent and in height. A sign of its height is that it is visible even from what are called "the deeps," the places ships sail into on their way into the lake, and further, its peaks are lit by the sun during a third of the night, both from the east and again from the west. A sign of its extent is that, having many regions in which many peoples dwell, and in which they say there are large lakes as well, they nevertheless say that all these regions are visible right up to its farthest peak. From the Pyrenees (this is a mountain toward the equinoctial west, in Celtica) flow the Ister and the Tartessus. The latter flows outside the Pillars, while the Ister flows through the whole of Europe into the Euxine Sea. Of the other rivers, most flow toward the north, out of the Hercynian mountains —
46| these being greatest in both height and number around this region. Right beneath the Bear itself, beyond the farthest reaches of Scythia, are the mountains called the Rhipaean, about whose size the accounts given are excessively legendary; at any rate most of the largest rivers, after the Ister, flow from there, so they say. Similarly around Libya, some rivers flow from the Ethiopian mountains — the Aegon and the Nysis — while the greatest of those named are the so-called Chremetes, which flows into the outer sea, and the first stream of the Nile, out of the mountain called the Silver Mountain. Of the rivers around the Greek region, the Achelous flows from Pindus, and the Inachus from there too, while the Strymon, the Nestus, and the Hebrus — three rivers — all flow from Scombrus; and many streams come from Rhodope as well. In the same way one could find the other rivers too flowing; but we have mentioned these by way of evidence. For indeed, even the rivers that flow out of marshes — the marshes themselves turn out to lie beneath mountains in almost every case, or beneath high places, fed by a gradual approach. That the origins of rivers, then, must not be thought to come about as if out of bounded cavities, is clear —
47| for the space of the earth would not be sufficient, so to speak, any more than that of the clouds, if what exists had to simply flow away, rather than one part departing while another part comes into being, forever being stored up anew out of what exists. And the fact that the springs lie beneath the mountains testifies to this: that by a slight coming-together, little by little, out of many seepages of moisture, the ground gives off water, and in this way the springs of rivers come into being. All the same, it is not at all strange that there should also be places holding a quantity of water, such as lakes — only not so large that the whole phenomenon could be explained by them, any more than if one supposed the visible springs to be the sources of the rivers; for most rivers flow, one might say, out of springs. So it is just as mistaken to think that the lakes are the entire body of water as to think this of the springs. That there are such chasms and openings in the earth is shown by rivers that get swallowed up. This happens in many places on the earth — in the Peloponnese, for instance, most such cases occur around Arcadia. The cause is that, being mountainous, it has no outlets from its hollows into the sea; for the places fill up, and having no outflow, find their own passage downward into depth, forced by the water pressing in from above.
48| Around Greece, then, such things happen only on a small scale altogether; but the lake below the Caucasus, which the people there call a sea, is a clear case. For this lake, though many great rivers flow into it, has no visible outflow, and discharges underground near the Coraxi, around what are called the "deeps" of the Pontus; these are a depth of sea that is virtually boundless — at any rate no one has ever yet been able, by letting down a line, to find its limit. At this point, then, some three hundred stades out from the land, it sends up drinkable water over a wide area — not continuously, but in three separate places. And around Liguria a river no smaller than the Rhone is swallowed up, and comes up again in another place; the Rhone itself is a river navigable by ships.
49| The same regions of the earth are not always either watered or dry, but they change according to the coming-into-being and the failing of rivers. That is why the arrangement of land and sea changes too, and it is not always the case that the same parts remain land while others remain sea for all time; rather, sea comes to be where there was dry land, and where there is now sea, there again comes to be land in turn. Still, one must think that these things happen according to a certain order and cycle. The origin and cause of this is that the interior of the earth, like the bodies of plants and animals, has a prime and an old age. Except that in plants and animals this does not happen part by part, but the whole must necessarily be at its prime and decline all together; whereas for the earth this happens part by part, on account of cooling and heating. These parts, then, grow and decline because of the sun and its revolution, and because of this the different parts of the earth take on differing power, so that up to a point they are able to remain well-watered, and then they dry out and grow old in turn; while other places come to life and become well-watered part by part in their turn. And it is necessary that, as places become drier, their springs disappear, and as this happens, the rivers first become small instead of great, and then in the end become dry; and as the rivers shift place, disappearing from some places and coming to be correspondingly in others, the sea changes as well —
50| for where the sea, pushed out by the rivers, kept overflowing as it receded, it is necessary that it turns the land dry there, while where it kept being enlarged and swelled by the streams' flow and was silted up and dried out, there again it comes to form a marsh instead. But because the whole of this natural process of change concerning the earth happens by gradual approach and over periods of time immensely long compared to our own lifetime, these changes go unnoticed, and whole peoples perish and are destroyed even before the change from beginning to end has been recorded. The greatest and swiftest destructions occur in wars; others come by diseases, others by failures of crops — and among these, some are great, others gradual, so that even the migrations of such peoples go unnoticed, because some leave their territories while others remain behind, up to the point when the land can no longer support any number of people at all. So it is likely that a long stretch of time passes from the first departure to the last, so that no one remembers it, but even among those who remain and are still preserved, the memory has been lost through the sheer quantity of time elapsed. In the same way one must suppose that it also goes unnoticed when the settlements of each people first began, in places that are changing and becoming dry after having been marshy and well-watered; for there too the change happens little by little over a long time, so that no one remembers who came first, or when, or in what condition the places were when they arrived — as indeed has happened also in the case of Egypt;
51| For this region too always appears to be growing drier, and the whole country is a deposit built up by the river, the Nile. But because as the marshes gradually dried out the people nearby kept settling them, the length of time involved has obscured the beginning of the process. At any rate, all the mouths of the river are plainly artificial and not the river's own, except the one, the Canobic mouth, and Egypt in ancient times was called Thebes. Homer bears this out too, even though he is, so to speak, quite recent relative to changes of this kind: for he makes mention of that place as though Memphis did not yet exist at all, or at least not as a place of such size. And it is reasonable that things happened this way: for the lower regions were settled later than the upper ones, since the places nearer the deposit are necessarily marshy for a longer time, because the water always collects more in the outermost parts. But this condition changes and the land flourishes again in turn: for as places dry out they come into good condition, while places that were formerly well-tempered become worse once they dry out too much. This is exactly what has happened in Greece, in the territory of Argos and Mycenae: at the time of the Trojan War the Argive land, being marshy, could support only a few people, while the Mycenaean land was in good condition (which is why it was held in greater honor), but now the reverse is true, for the reason just stated—
52| for the Mycenaean land has become barren and altogether dry, while the parts of the Argive land that were then unproductive because they lay under water have now become useful. So then, just as this has happened in this region, which is a small one, we must suppose the same thing happens with respect to large regions and whole countries as well. Now people who look only at a small scale think the cause of such conditions is a change in the universe as a whole, on the supposition that the heavens themselves come to be; that is why they say the sea is growing smaller, on the ground that it is drying up, because more places are now observed to have undergone this than before. But of these claims, part is true and part is not true: for it is true that there are more places that were formerly covered with water and are now dry land, but it is also true, on the other hand—for on looking about in many places people will find that the sea has advanced. But the cause of this should not be thought to be the coming-to-be of the universe: for it is absurd to move the whole on account of small and momentary changes, and the mass and size of the earth is surely nothing in comparison to the whole heaven. Rather, the cause of all these things must be supposed to be that they come about during fated periods of time, just as within the yearly seasons there is winter, so too within some great cycle there is a great winter and an excess of rains.
53| This does not always occur in the same places, but rather in the way that the so-called flood in the time of Deucalion did: for this too occurred especially around the Greek region, and of that region, especially around ancient Greece. This is the area around Dodona and the Achelous: for this river has often changed its course; for the Selli lived there, and those who were then called Graeci but are now called Hellenes. Whenever, then, such an excess of rains occurs, one must suppose that it lasts for a long time. And just as now, regarding the fact that some rivers are perennial and others are not, some say the cause is the size of the chasms underground, while we say it is the size of the high places and their density and coldness—for these receive the most water, and hold it, and produce it. but wherever the overhanging masses of the mountains are small, or porous and stony and clayey, we must suppose that those rivers give out sooner in this way—so that in whatever places such a movement of moisture occurs, it makes the wetness of those places more like a perennial supply. But with time these places, as this happens, dry out more, while the other, formerly watery places become fewer, until the onset of the same cycle comes round again.
54| Since it is necessary that some change occur in the universe as a whole, yet not coming-to-be and passing-away, if indeed the whole persists, it is necessary, as we say, that the same places are not always wet with sea and rivers and dry at other times. What actually happens makes this clear: for the Egyptians, whom we say are the most ancient of humans, their whole country plainly has come to be, and is, the work of the river. This is clear to anyone looking at the country itself, and the region around the Red Sea provides sufficient evidence: for one of the kings attempted to dig a canal through it (for it would have brought them no small advantages if the whole area became navigable; it is said that Sesostris was the first of the ancients to attempt it), but he found the sea to be higher than the land. For this reason he first, and Darius later, stopped digging, so that the river's current would not be ruined by the sea mixing into it. It is clear, then, that all these seas were one continuous sea. That is also why the region of Libya around Ammon appears lower and more hollow than the country below it would lead one to expect: for it is clear that once a deposit of silt had formed, marshes and dry land came about, and as time passed, the water that had been left behind and had formed a marsh, once dried out, is now simply gone.
55| Moreover, the region around Lake Maeotis has been so built up by the silting of the rivers that ships of much smaller size now sail in for trade than sixty years ago; so that from this it is easy to infer that this lake too, like most lakes, was originally the work of rivers, and that in the end it must all become dry land. Again, the Bosporus is constantly flowing because it is being silted up, and it is still possible to see with one's own eyes the manner in which this happens: for whenever the current formed a shoal running out from the Asian side, the water behind it would become a small marsh at first, then it dried up, and after this another shoal formed out from that one, and a marsh from that in turn; and this kept happening in the same way each time. And since this happens repeatedly, it is necessary that, as time goes on, this strait too become like a river, and in the end that this too become dry. It is evident, then, since time does not run out and the universe is eternal, that neither the Tanais nor the Nile has always flowed, but that the place from which they flow was once dry: for their work has a limit, but time does not. The same account will fit the other rivers as well.