Lecture 6 — Cause of the sea's saltiness according to Aristotle.

Since all the attempts to account for the saltiness 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 evaporation, one moist, the other dry, it is clear 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, too, 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 and the quantity of each of them are fixed, just as they are in the case of a flowing river or a burning flame. The answer is clear, and there is no doubt that the same account holds 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 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 facts which make it clear that this taste is due to the admixture of something. 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 proves this; for everything that is digested is condensed), and also sweat; in these then is excreted (along with other matter) an identical substance to which this flavor is due. The case of things burnt is analogous. What heat fails to assimilate becomes the excrementary residue in animal bodies, and, in things burnt, ashes.

That is why some people say that it was burnt earth that made the sea salt. 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 an undigested residue, like that of things burnt, consisting of this sort of earth. All the earthy stuff in the dry exhalation is of this nature, and it is the dry exhalation which accounts for its great quantity. Now since, as we have said, the moist and the dry evaporations 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 earth in rain. This process must always go on with such regularity as the sublunary 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 autumn, are brackish. The south is the warmest of winds and it blows from dry and hot regions. Hence it carries little moist vapor 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 evaporation from the places it passes over.) The north wind, on the other hand, coming from moist regions, is full of vapor and therefore cold. It is dry 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 is a dry wind in Libya. So the south wind charges the rain that falls with a great quantity of this stuff. Autumn rain is brackish because the 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 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 salt, but some part of its saltiness 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 sweet, and so the saltiness of the sea remains constant on the whole.

Salt water when it turns into vapor becomes sweet, and the vapor 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 become water. They all are water modified by a certain admixture, the nature of which determines their flavor. 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 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 from local causes (this must happen to sea and rivers alike). On the other hand the parts neither of the earth nor of the sea remain constant but only their whole bulk. For the same 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 saltiness 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 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 a filter. It is this stuff which make salt water heavy (it weighs more than fresh water) and thick. The difference in consistency is such that ships with the same cargo very nearly sink in a river when they are quite fit to navigate in the sea. This circumstance has before now caused loss to shippers freighting their ships in a river. That the thicker consistency is due to an admixture of something is proved 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 earthy matter is there in the 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, this would bear out what we have said. They say that this lake is so bitter and salt that no fish live in it and that if you soak clothes in it and shake them it cleans them. The following facts 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 neighboring 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 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 added freely gives a sweet taste, 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 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 them was extinguished but the earth through which they percolate preserves the character of lye or ashes. Springs and rivers with all kinds of flavors are found in many places. These flavors must in every case be due to the fire that is or was in them, for if you expose earth to different degrees of heat it assumes various kinds and shades of flavor. It becomes full of alum and lye and other things of the kind, and the fresh water percolates through these and changes its character. 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 neighborhood 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. These differences are explained by a knowledge of the particular mixtures that determine different savors. But these have been explained in another treatise.

We have now given an account of waters and the sea, why they persist, how they change, what their nature is, and have explained most of their natural operations and affections.

170. Having rejected these theories about the salt of the sea, he now presents his own opinion. About this he does three things:

first, he prefaces some things needed for manifesting the proposition;

second, he assigns the cause of the sea's saltiness, at this being so we must go on to try to explain (358a3);

third, he manifests what he had said through signs, at there is more evidence to prove (358b34).

In regard to the first he does two things (357b23).

The first item he repeats from the foregoing is that exhalations are of two kinds: one is moist and the other dry; and this must be regarded as the source of these, i.e., of the sea's saltiness.

second, he raises a problem whose true solution must be seen before the proposition is manifested. The problem is this: do the parts of the sea always remain numerically the same or are they changed in number while remaining the same according to quantity, as happens in air and in the drinkable water of rivers and in fire? For in all these the parts become other and other in number, but the species or form of the aggregate of these parts remains the same; and this is especially evident in flowing waters and in a burning flame, which is forever being renewed by successively new fumes, as was said above, and yet the flame always remains the same numerical one. Hence it is probable that all these cases are not exactly the same, for there is at least a difference so far as the rapidity of change is concerned: for it is plain that the parts of a flowing stream are exchanged more rapidly than the parts of the earth. Yet in all these cases there is a generation and corruption according to parts, following a certain order.

171. Then when he says, this being so we must go on to try to explain (358a3), he assigns the cause of the sea's salt. About this he does two things:

first, he shows in general from what source a salty savor is produced;

second, from what source is derived the saltiness of the sea, at that is why some people say (358a14).

He says therefore first (358a3) that, since the above are as described, there is need to set forth the cause of the sea's saltiness. For it is plain by many signs that the salty taste is caused by an admixture of something. For we see that, in the bodies of animals, what is most undigested is salty and bitter: this is especially the residue of food, and more especially the residue collected in the bladder. That this is least digested is indicated by the fact that it is the most refined of all the residues, whereas all digested things are seen to be thickened by heat. And as with urine, so with sweat: for likewise with sweat, something undigested is separated which gives it this taste. So too with burnt things: because whatever is left after the action of the heat, that the heat cannot overcome, becomes a residue in the bodies of animals, and ash in burned objects, which, if mixed with water, makes it salty and bitter.

172. Then when he says, that is why some people say (358a14), he assigns the specific cause of the sea's saltiness. About this he does three things:

first, he does what is said;

second, he manifests this through certain signs, at it also explains why rain that comes from the south (358a27);

third, he excludes some objections, at the action of this cause is continually making the sea (358b12).

He says therefore first (358a14) that since a salty and bitter taste is found to be caused by the admixture of something undigested or burnt, some have said that the sea was formed out of charred earth. But this is unacceptable if taken in a literal sense; taken as a metaphor, however, namely, in the sense that the saltiness in the sea is caused by a mixing with something akin to charred earth, then it is true. For just as it occurs in the aforesaid, namely, in urine, sweat and ashes, so it must be understood even in regard to the earth as a whole: just as burning objects leave a residue of certain items that the fire was unable to dissolve, so too we must understand something to be left with respect to the earth by the action of heat, similar to the ash left by the action of fire.

An example of this is the exhalation arising out of dry land, the magnitude of which the earth shows. Now when a dry exhalation of this sort mixes with the moist exhalation that is condensed into clouds and rain, it is necessary that in that moist exhalation there be contained something of the power of that dry exhalation; as a consequence, both mixed together re-descend when it rains.

But this always occurs in a definite order: the mingled exhalations are borne aloft and re-descend in the form of rain. I say that this takes place in a definite order, i.e., to the extent that things occurring in the lower regions can participate in order: for they do not participate in order so perfectly as to occur always in the same way as do the heavenly bodies, but so as to occur for the most part. And thus he concludes that this sets forth whence there is generation of salt in the water of the sea.

173. Then when he says, it also explains why rain that comes from the south (358a27), he manifests what he had said through certain signs. And he says that because the dry exhalation mixes with the moist evaporation, southern waters and the first waters to fall in autumn are brackish, i.e., heaver and more on the salty side. First he explains this with respect to southern waters, i.e., which fall with the south wind blowing. For the south wind in its blowing and in its size is very warm: for it blows from regions that are hot and dry and have little moisture—that is why it is a hot wind. But because one could say that it blows from a cold region, namely, from the antarctic pole, which must be cold on account of its distance from the sun, he adds that, even supposing that it blows, not from the hot, but from the cold places, nevertheless it must travel toward us through regions close to us that are hot and dry, as to proximate regions: hence it is hot.

But the north wind, which comes to us directly from cold regions, collects many moist and cold vapors along with it: therefore, it is a cold wind. Yet for us it brings clear weather, because it drives these vapors in the opposite direction; but in places and regions in the south it is a wet wind, because that is where it drives the vapors. Conversely, a south wind is clear for those who live in the south, namely, around Libya, but for us it is rainy. And so, because a south wind collects a large quantity of dry exhalation, such a wind contributes a great deal to the falling of water that is salty. Thus is made plain the reason for one of the statements, namely, why rains from the south are brackish.

But because the same was said of the first rains of autumn, he also assign as cause for this: it is necessary that the heaviest constituents of the vapors carried aloft descend first; but the heaviest are those containing the most earth; and that is why the first waters to fall in autumn after the summer are brackish and have a great deal of what is earthy.

He gives another sign in support of the reason assigned as the cause of saltiness, namely, that the reason why the sea is warm and the regions near the sea are comparatively warmer is due to the abundance of the above-mentioned exhalation mixed with the water of the sea. For things previously afire are seen to possess within themselves the virtue of heat even after the fire has gone out: this is plain in ashes and lime and the excrement of warm-bellied animals. The reason for this is that the virtue of the alterating heat remains in them along with the dry exhalation. Hence, since he had said that the cause of the saltiness of the sea was the dry exhalation resolved from dried-out earth, it follows that the sea will also derive an abundance of warmth therefrom.

174. Then when he says, the action of this cause is continually making the sea (358b12), he excludes some doubts on the aforesaid. About this he does two things:

first, he excludes the doubts;

second, from what has gone before he concludes to the cause of the saltiness of the sea, at for the present let us say this (358b23).

The first is divided into two parts according to the two doubts solved.

The first doubt (358b12) is that since the water of the sea does not continue to have numerically the same parts but evaporates and re-descends, it does not seem that the cause of the saltiness of the sea is the mixed-in dry exhalation, but rather an evaporation from salt water.

To remove this doubt he says that the water of the sea is forever becoming other and other as to its parts, and each part has in its generation the aforesaid cause of saltiness, namely, the admixture of the earthy exhalation. Now it is also true that some part of the salt water is always being borne aloft with the sweet through evaporation — but since something refined evaporates more quickly than something dense, and the sweet is more refined than the salty, necessarily less of the salty than of the sweet is elevated; but through being mixed with the dry exhalation the sweet again grows in saltiness, and thus the sea is forever maintained constant both in quantity and in salt. And this is said of the sea as a whole, i.e., so far as the whole sea is concerned, it is kept constant or practically so—for the aforesaid quantity is not always kept absolutely exactly.

175. The solution of the second doubt is at salt water when it turns into vapor becomes sweet (358b16). The doubt is this: since the water of the sea is salty, what accounts for the fact that sweet water is generated from the vapors resolved from the waters of the sea?

To answer this he says that we must repeat that what evaporates in the sea becomes, when it is condensed, drinkable and sweet; therefore, it is not converted back into sea, i.e., into salt water, but into fresh water. This happens to other things: wine and all liquids, when they are condensed, are turned into simple water: for when they evaporate, their condensed vapors are turned into water. The reason for this is that the principle of all moisture is water, and all things are resolved into their principles. Now all other liquids are generated from water which is affected or altered in some way, which affections vary according to the ingredients, and the savor depends on what is mixed in. This explains why, in the process of being generated, water varies and becomes salty. But because each thing is resolved into its principle absolutely, as has been said, the consequence is that whether it is salty sea water, or any liquid whatsoever of any vapor [savor?] you wish, the product of evaporation is simple water.

176. Then when he says, for the present let us say this (358b23), from all the foregoing he gathers the cause of the salt of the sea. And he says that we must now say that some portion of the water of the sea is forever being raised aloft by evaporation and becomes drinkable when it is condensed; and further, that with the falling water there descends something terrestrial which was borne aloft, not from the water of the sea, but from dry land. And this terrestrial element because of its weight, sinks below the drinkable and sweet portion, with the result that the finer portion evaporates more. And therefore, as a result of continuous generation and evaporation, neither the sea nor rivers disappear: unless they happen to disappear in certain regions according to certain definite cycles, as mentioned earlier. Moreover, neither do the same parts of the sea or of the earth always remain, but only the whole bulks of both. Thus, we must think of the earth as we do of the sea, namely, that one part is borne aloft through exhalation and another part descends and, furthermore, that the parts on the surface exchange places with those that descend: as a result, every part of both can be corrupted and generated.

It should be noted that Aristotle, in assigning the cause of the saltiness of the sea when treating of the natural place of water above, stated that the saltiness of the sea is caused by the evaporation of what is fine and sweet. But this would not be a cause, if nothing foreign were mixed in the sea water—since it would be necessary that what remained be sweet and drinkable, according to the nature of simple water. Consequently, in order to show how the water of the sea is salty, he shows that something foreign is mixed in it, which sinks (after the sweet potable water is elevated) and makes the water of the sea salty. On this account he says that burnt earth is mixed with the vapors from which water is generated. Hence, since each part of the sea is thus generated, it follows that a terrestrial adjunct of this sort is mixed with every part of the sea, and generally sinks below the sweet and fine, the major portion of which is elevated. And because sweet water is generated out of what evaporates, and all the water of springs and rivers is generated out of what evaporates, either on the surface of the earth or below the earth, it follows that the water of springs and rivers is sweet, simply because they are close to the source of generation; but the water of the sea is salty, being both the residue of vapors elevated by the sun and the final terminus into which the generated water is collected.

177. Then when he says, there is more evidence to prove (358b34), he manifests that the salty savor is caused from a terrestrial mixture. And he gives many signs.

The first of these concerns a waxen container sealed and set in water. Whatever seeps in becomes sweet, as though the terrestrial stuff were filtered out by the wax.

Another sign is that sea water is heavier than the sweet.

A third sign is that sea water is denser than river water, so that ships laden with cargo sink deeper in rivers than in the sea.

The fourth sign is that eggs, if full, float in water to which salt has been added and even float in the sea. Hence the sea seems to be like mud on account of its density. Those who make brine take as a sign that the salt has been well mixed with the water, when eggs float on it. Therefore, sea water, too, is dense on account of an admixture of some gross earthy stuff.

The fifth sign is that in the lake in Palestine which is salty or bitter, if anyone should immerse a man or ass, it does not sink; and clothing dipped in it becomes fetid.

The sixth sign concerns a spring of broad, i.e., salt, water in the province of Chaonia. This spring flows into a river of fresh water in which are no fish, but on account of the mixture contributed by this spring, salt is sometimes found instead of fish. When this water is boiled, salt is left after what is hot and liquid has evaporated. These salts are not coarse but fine as snow; they are weaker than other salts and give greater pleasure in foods.

The seventh sign is that there is a region in which reeds and rushes are burned. When their ash is cooked in water and cooled, it becomes salty to a degree depending on the proportion of burned earthy matter, which he had said is the cause of saltiness. Hence, both in the water of these ashes, as well as in the water of the sea, there must be a combustion which causes saltiness. This is why universally any flowing water of springs and rivers which is salty, was once hot, as though proceeding from ignited earth. Afterwards the fire is extinguished within the earth, which, by the burning, having become sulphurous or something of the sort, still retains the marks of having been burnt, as lime and ashes do—so that water passing through it becomes salty. Indeed, such water not only becomes salty and receives saltiness from the earth through which it passes, but also other savors, as he explains with examples (and this is plain in the text).

Finally, he sums up what has been said—and this is also plain in the text.