[5] To return to the saltness of the sea: those who create the sea once for all, or indeed generate it at all, cannot account for its saltness. It makes no difference whether the sea is the residue of all the moisture that is about the earth and has been drawn up by the sun, or whether all the flavour existing in the whole mass of sweet [10] water is due to the admixture of a certain kind of earth. Since the total volume of the sea is the same once the water that evaporated has returned, it follows that it must either have been salt at first too, or, if not at first, then not now either. If it was salt from the very beginning, then we want to know why that was so; and why, if salt water was drawn up then, that is not the case now.
[15] Again, if it is maintained that an admixture of earth makes the sea salt (for they say that earth has many flavours and is washed down by the rivers and so makes the sea salt by its admixture), it is strange that rivers should not be salt too. [20] How can the admixture of this earth have such a striking effect in a great quantity of water and not in each river singly? For the sea, differing in nothing from rivers but in being salt, is evidently simply the totality of river water, and the rivers are the vehicle in which that is carried to their common destination.
It is equally absurd to suppose that anything has been explained by calling the sea ‘the sweat of the earth’, like Empedocles. Metaphors are poetical and so that [25] expression of his may satisfy the requirements of a poem, but as to knowledge of nature it is unsatisfactory. Even in the case of the body it is a question how the sweet liquid drunk becomes salt sweat—whether it is merely by the departure of some [30] element in it which is sweetest, or by the admixture of something, as when water is strained through ashes. Actually the saltness seems to be due to the same cause as in the case of the residual liquid that gathers in the bladder. That, too, becomes bitter and salt though the liquid we drink and that contained in our food is sweet. If then the bitterness is due in these cases (as with the water strained through lye) to the [357b1] presence of a certain sort of stuff that is carried along by the urine (as indeed we actually find a salt deposit settling in chamber-pots) and is secreted from the flesh in sweat (as if the departing moisture were washing the stuff out of the body), then [5] no doubt the admixture of something earthy with the water is also what makes the sea salt.
Now in the body stuff of this kind, viz. the sediment of food, is due to failure to digest; but how there came to be any such thing in the earth requires explanation. Besides, how can the drying and warming of the earth cause the secretion of such a [10] great quantity of water; especially as that must be a mere fragment of what is left in the earth? Again, waiving the question of quantity, why does not the earth sweat now when it happens to be in process of drying? (For the moisture and the sweat are bitter.) For if it did so then, it ought to do so now. But it does not: on the contrary, [15] when it is dry it grows moist, but when it is moist it does not secrete anything at all. How then was it possible for the earth at the beginning when it was moist to sweat as it grew dry? Indeed, the theory that maintains that most of the moisture departed and was drawn up by the sun and that what was left over is the sea is more [20] reasonable; but for the earth to sweat when it is moist is impossible.
Since all the attempts to account for the saltness of the sea seem unsuccessful let us explain it by the help of the principle we have used already.
Since we recognize two kinds of exhalation, one moist, the other dry, it is clear [25] that the latter must be recognized as the source of phenomena like those we are concerned with.
But there is a question which we must discuss first. Does the sea always remain numerically one and consisting of the same parts, or is it one in form and volume while its parts are in continual change, like air and sweet water and fire? All of these are in a constant state of change, but the form of the quantity of each of them [30] is fixed, just as in the case of a flowing river or a burning flame. The answer is clear, and it is plausible that the same account must hold good of all these things alike. They differ in that some of them change more rapidly or more slowly than others; and they all are involved in a process of perishing and becoming which yet affects [358a1] them all in a regular course.
This being so we must go on to try to explain why the sea is salt. There are many signs which make it clear that this taste is due to the admixture of something. [5] First, in animal bodies what is least digested, the residue of liquid food, is salt and bitter, as we said before. All animal excreta are undigested, but especially that which gathers in the bladder (its extreme lightness indicates this; for everything [10] that is digested is condensed), and also sweat; in these then is excreted (along with other matter) an identical substance to which this flavour is due. The case of things burnt is analogous. What heat fails to overcome becomes the excrementary residue in animal bodies, and, in things burnt, ashes. That is why some people say that the [15] sea itself was made from burnt earth. To say that it was burnt earth is absurd; but to say that it was something like burnt earth is true. We must suppose that just as in the cases we have described, so in the world as a whole, everything that grows and is naturally generated always leaves a residue, like that of things burnt, consisting of [20] this sort of earth, and all exhalation on dry land is of this nature; for it is this which accounts for its great quantity. Now since, as we have said, the moist and the dry exhalations are mixed, some quantity of this stuff must always be included in the clouds and the water that are formed by condensation, and must redescend to the [25] earth in rain. This process must always go on with such regularity as this world admits of, and it is the answer to the question how the sea comes to be salt.
It also explains why rain that comes from the south, and the first rains of [30] autumn, are brackish. The south is the warmest of winds, both in size and strength, and it blows from dry and hot regions. Hence it carries little moist vapour and that is why it is hot. (It makes no difference even if this is not its true character and it is originally a cold wind, for it becomes warm on its way by incorporating with itself a great quantity of dry exhalation from the places it passes over.) The north wind, on the other hand, coming from moist regions, is full of vapour and therefore cold. It [358b1] brings fine weather in our part of the world because it drives the clouds away before it, but in the south it is rainy; just as the south in Libya. So the rain that falls is charged with a great quantity of this stuff. Autumn rain is brackish because the [5] heaviest water must fall first; so that that which contains the greatest quantity of this kind of earth descends quickest.
This, too, is why the sea is warm. Everything that has been exposed to fire contains heat potentially, as we see in the case of lye and ashes and the dry and [10] liquid excreta of animals. Indeed those animals which are hottest in the belly have the hottest excreta.
The action of this cause is continually making the sea more brackish, but some part of it is always being drawn up with the sweet water. This is less than the sweet water in the same ratio in which the salt and brackish element in rain is less than the [15] sweet, and so the saltness of the sea remains constant on the whole. When it turns into vapour it becomes sweet, and the vapour does not form salt water when it condenses again. This I know by experiment. The same thing is true in every case of the kind: wine and all fluids that evaporate and condense back into a liquid state [20] become water. They all are water modified by a certain admixture, the nature of which determines their flavour. But this subject must be considered on another more suitable occasion.
For the present let us say this. The sea is there and some of it is continually being drawn up and becoming sweet; this returns from above with the rain. But it is [25] now different from what it was when it was drawn up, and its weight makes it sink below the sweet water. This process prevents the sea, as it does rivers, from drying up except locally (this must happen to sea and rivers alike); nor do the parts either of the earth or of the sea remain constant but only their whole bulk. (For the same [30] thing is true of the earth as of the
sea.) Some of it is carried up and some comes down with the rain, and both that which remains on the surface and that which comes down again change their situations.
There is more evidence to prove that saltness is due to the admixture of some substance, besides that which we have adduced. Make a vessel of wax and put it in the sea, fastening its mouth in such a way as to prevent any water getting in. Then [359a1] the water that percolates through the wax sides of the vessel is sweet, the earthy stuff, the admixture of which makes the water salt, being separated off as it were by [5] a filter. It is this stuff which makes salt water heavy (it weighs more than fresh water) and thick. The difference in consistency is such that ships with the same weight of cargo very nearly sink in a river when they are quite fit to navigate in the sea. Ignorance of this has before now caused loss to shippers freighting their ships in [10] a river. That the bulk is more dense when something23 is mixed in is indicated by the fact that if you make strong brine by the admixture of salt, eggs, even when they are full, float in it. It almost becomes like mud; such a quantity of matter is there in the [15] sea. The same thing is done in salting fish.
Again if, as is fabled, there is a lake in Palestine, such that if you bind a man or beast and throw it in it floats and does not sink beneath the water, this would bear out what we have said. They say that this lake is so bitter and salt that no fish live in [20] it and that if you soak clothes in it and shake them it cleans them. The following signs all of them support our theory that it is some earthy stuff in the water which makes it salt. In Chaonia there is a spring of brackish water that flows into a [25] neighbouring river which is sweet but contains no fish. The local story is that when Heracles came from Erytheia driving the oxen and gave the inhabitants the choice, they chose salt in preference to fish. They get the salt from the spring. They boil off [30] some of the water and let the rest stand; when it has cooled and the heat and moisture have evaporated together it gives them salt, not in lumps but loose and light like snow. It is weaker than ordinary salt and must be added freely for seasoning, and it is not as white as salt generally is. Another instance of this is found in Umbria. There is a place there where reeds and rushes grow. They burn some of [359b1] these, put the ashes into water and boil it off. When a little water is left and has cooled it gives a quantity of salt.
Most salt rivers and springs must once have been hot. Then the original fire in [5] them was extinguished but the earth through which they percolate preserves the character of lye or ashes. Springs and rivers with all kinds of flavours are found in many places. These flavours must in every case be due to the fire that is present or produced in them; for if you expose earth to different degrees of heat it assumes [10] various kinds and shades of flavour. It becomes full of alum and lye and other things of the kind, and the fresh water percolates through these and changes its character. [15] Sometimes it becomes acid as in Sicania, a part of Sicily. There they get a salt and acid water which they use as vinegar to season some of their dishes. In the neighbourhood of Lyncus, too, there is a spring of acid water, and in Scythia a bitter spring. The water from this makes the whole of the river into which it flows bitter. [20] These differences are explained by a knowledge of the particular mixtures that determine different savours. But these have been explained in another treatise.
We have now given an account of water and the sea, why they always persist, [25] how they change, what their nature is, and have explained their natural operations and affections.
4 · Let us proceed to the theory of winds. Its basis is a distinction we have already made. We recognize two kinds of exhalation, one moist, the other dry. The [30] former is called vapour: for the other there is no general name but we must call it a sort of smoke, applying to the whole of it a word that is proper to one of its forms. The moist cannot exist without the dry nor the dry without the moist: whenever we speak of either we mean that it predominates. Now when the sun in its circular course approaches, it draws up by its heat the moist evaporation: when it recedes the [360a1] cold makes the vapour that had been raised condense back into water which falls and is distributed over the earth. (This explains why there is more rain in winter and more by night than by day: though the fact is not recognized because rain by night is [5] more apt to escape observation than by day.) But there is a great quantity of fire and heat in the earth, and the sun not only draws up the moisture that lies on the surface of it, but warms and dries the earth itself. Consequently, since there are two kinds of exhalation, as we have said, one like vapour, the other like smoke, both of [10] them are necessarily generated. That in which moisture predominates is the source of rain, as we explained before, while the dry one is the source and substance of all winds. That things must necessarily take this course is clear from the facts [15] themselves, for the exhalations must necessarily differ; and the sun and the warmth in the earth not only can but must produce them.
Since the two are specifically distinct, wind and rain obviously differ and their [20] substance is not the same, as those say who maintain that one and the same air when in motion is wind, but when it condenses again is water. Air, as we have explained in an earlier book, is made up of these as constituents. Vapour is moist and cold (for its fluidity is due to its moistness, and because it derives from water it is naturally cold, [25] like water that has not been warmed); whereas smoke is hot and dry. Hence each contributes a part, and air is moist and hot. It is absurd that this air that surrounds us should become wind when in motion, whatever be the source of its motion—on [30] the contrary the case of winds is like that of rivers. We do not call water that flows anyhow a river, even if there is a great quantity of it, but only if the flow comes from a spring. So too with the winds; a great quantity of air might be moved by the fall of some large object without flowing from any source or spring.
The facts bear out our theory. It is because the exhalation takes place uninterruptedly but differs in degree and quantity that clouds and winds always [360b1] appear in their natural season; and it is because there is now a great excess of the vaporous, now of the dry and smoky exhalation, that some years are rainy and wet, others windy and dry. Sometimes there is much drought or rain, and it prevails over [5] a continuous stretch of country. At other times it is local; the surrounding country often getting seasonable or even excessive rains while there is drought in a certain part; or, contrariwise, all the surrounding country gets little or even no rain while a [10] certain part gets rain in abundance. The reason for all this is that while the same affection is generally apt to prevail over a considerable district because adjacent places (unless there is something special to differentiate them) stand in the same relation to the sun, yet sometimes the dry exhalation will prevail in one part and the [15] moist in another, and sometimes the reverse. Again the reason for this latter is that each exhalation goes over to that of the neighbouring district: for instance, the dry evaporation circulates in its own place while the moist migrates to the next district or is even driven by winds to some distant place; or else the moist remains and the [20] dry moves away. Just as in the case of the body when the stomach is dry the lower belly is often in the contrary state, and when it is dry the stomach is moist and cold, so it often happens that the exhalations reciprocally take one another’s place and [25] interchange.
Further, after rain wind generally rises in those places where the rain fell, and when rain has come on the wind ceases. These are necessary effects of the principles [30] we have explained. After rain the earth is being dried by its own heat and that from above and gives off the exhalation which we saw to be the body of the wind. And whenever this separation occurs and winds prevail, then when they drop (since the heat is continually being separated and rising to the upper region), then the fall in temperature makes vapour form and condense into water. Water also forms and cools the dry exhalation when the clouds are driven together and the cold [361a1] concentrated in them. These are the causes that make wind cease on the advent of rain, and rain fall on the cessatio
n of wind.
The cause of the predominance of winds from the north and from the south is [5] the same. (Most winds, as a matter of fact, are north winds or south winds.) These are the only regions which the sun does not visit: it approaches them and recedes from them, but its course is always over the west and the east. Hence clouds collect on either side, and when the sun approaches it provokes the moist exhalation, and [10] when it recedes to the opposition side there are storms and rain. So summer and winter are due to the sun’s motion to and from the solstices, and water ascends and falls again for the same reason. Now since most rain falls in those regions towards [15] which and from which the sun turns and these are the north and the south, and since most exhalation must take place where the earth receives the greatest rainfall, just as green wood gives most smoke, and since this exhalation is wind, it is reasonable that the most and most important winds should come from these quarters. (The [20] winds from the north are called Boreae, those from the south Noti.)
The Complete Works of Aristotle Page 103