by Aristotle
38 · Why is it that the sea, which is heavier than fresh water, is more transparent? Is it because of its fattier composition? Now oil poured on the surface [20] of water makes it more transparent, and the sea, having fat in it, is naturally more transparent. Or is that which is lighter not always more transparent also? For oil itself is lighter than water but not more transparent. Or is the sea not really more transparent, but only apparently so? For fresh water comes from the earth or from streams, and its source sends forth earth also with the water, so that the streams, not [25] being pure, bring down with them the earth and sediment. This then is the reason why fresh water is less transparent.
39 · Why do the bowels of those who swim in the sea open readily? For if it is because they take violent exercise, those who run also take very violent exercise, yet their bowels do not open. Or does not every form of exertion cause the bowels to [30] open, but only such exercise as does not cause liquefaction? Now staying in the sea seems to make men, generally speaking, hungrier and opens the bowels; for the vapour given off by it is both hot and dry.
40 · Why does the Lake of Paesus,15 of which the water is fresh, wash and also remove the stains from garments? For water which is sweet washes, but that [35] which is bitter removes stains, and water cannot have both these qualities at the same time. Are stains removed not because the water is bitter, but by the quality of stickiness which has this power? Hence animals’ hoofs have this effect, and anything which contains mucous matter; and so also any bitter substances which partake of this character do the same. Now in this lake it so happens that the bitter [936a1] element of the quality of soda has been burnt out, but the fatty and sticky element remains. It is by virtue of this that it removes stains, and it washes because it is fresh.
41 · Why does the part of the sea which is calm appear white, while that [5] which is agitated appears black? Is it because that which is less visible appears blacker, and water which is in motion is less seen than that which is still? Or is it because that which is transparent is white, while that which is not so is black, and that which is in motion is less transparent? [10]
BOOK XXIV
PROBLEMS CONCERNING HOT WATER
1 · Why is it that, if one is anointed with oil, hot water poured over one seems less hot, in spite of the fact that oil contains heat? Is it because owing to the smoothness caused by the oil the water glides off and sinks in less? [15]
2 · Why is it that in the summer the water in wells becomes warm after midday? Is it because by that hour the heat has mastered the air, whereas before midday the heat is dissolving and putting an end to the cold; but the one does not [20] prevail as soon as the other has ceased, but only after time has elapsed?
3 · Why is it that water, which sometimes becomes hotter than a flame, does not burn wood, whereas the flame does so? Is it because the flame, and the breath which comes from it, consist of small particles, whereas water is made up of large particles and so does not penetrate? Now flame and the heat from coals owing to [25] their rarity can penetrate and destroy.
4 · Why is it that boiling water has not the power to melt, while the stomach possesses this power? Is it because the heat which is in the stomach penetrates owing to its rarity, whereas water cannot penetrate because of its density? Or is it because liquid prevents other things also from melting (for nothing melts in liquid)? [30] In the stomach, however, the liquid flows down into the bladder and so permits the process of melting.
5 · Why is it that the bottom of a vessel containing boiling water does not burn, but one can carry it holding it by the bottom, whereas if the water be removed it burns? Is it because the heat as it is engendered in the bottom of the vessel is [35] extinguished by the water? That is also why substances which can be melted do not melt if any liquid is added to them.1
6 · Why is it that water does not boil over so much in winter as in summer, although heated not only up to the same temperature but even higher, and although [936b1] equally hot or even hotter? Is it because boiling over is due to the rising of bubbles? The water then itself becomes just as hot in winter as in summer,2 but the bubbles cannot rise to the same extent, because the surrounding air is cold, but they rise [5] smaller in size, being compressed by the cold, and soon burst, being broken by the air. They are, therefore, smaller in bulk and fewer in number in the winter, and the contrary in summer. Now boiling over is due to the number and size of the bubbles forming the froth.
[10] 7 · Why does hot water cause wrinkles, but fire, though it is hot, not do so? Is it because fire produces breath and so causes swelling (for it distends the skin), whereas it is the curving of the skin which makes wrinkles?
8 · Why is it that the bottoms of vessels in which water is being heated are hotter while the water is still cold? Is it because, while the water is still cool, the heat [15] is enclosed and driven inwards, being prevented from making its way out, but, when the water in the vessel becomes thoroughly heated, since the fire no longer holds the heat but expends itself and becomes less, the bottom of the vessel becomes cooler, just as a bath does? For a bath is hotter in winter than in summer, because the heat [20] is more enclosed in winter than in summer by the surrounding air which is cold.
9 · Why is it that water when it boils does not form a scum, as do pea-soup and lentil-soup? And yet water is lighter than these, and light substances ought to be able to project themselves more easily to a distance. The same thing happens in the case of silver when it is being purified; for those who clean out the mint make [25] gains by appropriating the remnants, sweeping up the silver which is scattered about. Is it because the heat causes the scum by vaporizing and subjecting to force anything which opposes its own natural impetus? Water, therefore, owing to its [30] lightness and rarity is not subjected to force, and so no great heat is collected in it, but the heat which continually passes into it cuts its way through before it can become massed together. But substances which have body in them, like thick soups and silver, since, owing to their weight, they contain much corporeal matter and offer resistance,3 because they are subjected to violent force as the heat tries to [35] make its way out, form bubbles wherever the heat prevails; for, owing to their density, the heat cannot pass through them, but the density prevails until it is thrown off by the heat which flows into it. The result is a sudden impact, and not a continuous pressure, owing to the heat passing up quickly from below.
10 · Why, if substances are moistened in hot water for a short time, do they [937a1] swell, but, if for a long time, collapse and become wrinkled? Is it because the heat makes a thing liquid instead of solid and produces breath from liquid and rarefies what is dense? At first, therefore, it heats things which are solid and makes them moister, and producing breath from the moisture distends and swells them; but [5] when it heats them still more, it rarefies their outer part,4 so that the vapour is given off, and the drying up of moisture causes their bulk to collapse. Now, as anything collapses, its outer skin shrivels up, and where it shrivels up unevenly, wrinkles are formed. [10]
11 · Why are stones formed by hot water rather than by cold? Is it because a stone is produced from the failure of moisture, and moisture fails more through the operation of heat than of cold, in other words petrifaction is the result of heat—as Empedocles says that both rocks and stones come into being through the action of5 [15] hot waters? Or, while it is true that heat petrifies, can petrifaction also take place through cold, because an extremely hard frost consumes the moisture and causes hardening? That cold, pure and simple, produces this effect is clear from the fact that its excess does so.
12 · Why is it that if one has one’s foot in hot water, if the foot is kept still [20] the water appears to be less hot, but hotter if it is moved? Does the same thing happen as in the body, viz. that, when one runs in the wind, the opposing air becomes increasingly colder, and the farther one goes the more one notices it?
[25] 13 · Why do hot things cool off more in the sun than in the shade? Is it because the lesser
heat is destroyed by the greater? Or is it because in the shade the surrounding cold represses the interior heat and does not allow it to make its way out, producing the same effect as the pouring of cold water produces upon those who [30] are fainting6 (for it encloses the heat and prevents it from escaping); and speaking generally the interior parts of anything are warmer in the winter? But in the sun, since there is nothing which intercepts it, the heat is free to move and vanishes more quickly.
14 · Why is it that water heated by the sun is not more wholesome for [35] washing purposes? Is it because, owing to the fact that it is cooling, it causes shivering while it is still upon the body?7 Or, while it has this effect, is it unhealthy if used often for washing? For hot water, generally speaking, produces concoction and has a drying effect, whereas cold water has an astringent effect, and so both do [937b1] good. Therefore cold water and water heated over a fire are both beneficial to those who wash in them; but water heated by the sun owing to the weakness of its heat produces the effect of neither of these, but merely has the effect of moistening—like the light of the moon.
[5] 15 · Why is water which has been heated in the sun not wholesome? Is it because that which is cooling causes shivering?
16 · Why are the hot waters at Magnesia and at Atarneus fresh? Is it because more water pours into the hot water as it flows out, and so its saltness [10] disappears, but its heat remains?
17 · Why is it that in Magnesia the hot waters ceased to be hot but the water remained salty? Is it because more cold water from elsewhere was poured at the same time into the springs and extinguished the heat? Now the earth was salty, but [15] not hot owing to the abundance of water flowing into it. (A similar process occurs in water which is strained through hot ashes; for the water being strained through the hot ashes cools the ashes and itself becomes cold, but is salty and bitter owing to the ashes.) But when the water which was added had become transformed, the heat in [20] the earth for a different reason prevailed over the coldness of the water owing to its small volume, and hot waters flowed again.
18 · Why are waters from hot springs all salty? Is it because they usually percolate through earth which contains alum (as is shown by the smell of the water) and has been burnt? Now the ashes of anything are salty and smell of sulphur. The earth therefore burns the water like a thunderbolt. Many hot springs therefore are [25] due to strokes of thunderbolts.
19 · Why are hot bathing-places sacred? Is it because they are due to two very sacred things, sulphur and the thunderbolt?
BOOK XXV
PROBLEMS CONNECTED WITH THE AIR
1 · Why is it that pain is caused if the limbs are enclosed in inflated skins? Is [30] it due to the pressure of the air? For just as the air does not yield to pressure applied to the skin from outside but repels it, so the air also presses upon the limbs enclosed within. Or is it because the air is held within by force and is compressed, and so, [35] having naturally an outward impetus in every direction, it presses against the body enclosed within?
2 · Why is it that in marshes near rivers the so-called ‘bellowings’ take place, which according to the fable are uttered1 by the sacred bulls of the god? That which is produced is certainly a noise which resembles the roaring of a bull, so much so [938a1] that it has the same effect on cows when they hear it as the bellowing of a bull. Is it due to the fact that this phenomenon always occurs wherever rivers stagnate into marshes,2 or are driven back by the sea, or give forth wind in unusually large quantities? The reason is that hollows in the earth form, and the water making its [5] way in (for there is always a flow of water in marshy ground of this kind) thrusts the air also through a narrow entrance into a wider hollow, just as a noise like roaring is produced if one makes a sound through the aperture into an empty jar; for it is by a similarly shaped organ that a bull’s roaring is produced. Now, if the hollows have [10] irregular forms, a variety of strange noises is produced; for if one takes off the lid of a vessel and rubs it against the bottom, drawing it in and out,3 it makes enough noise to frighten away wild animals when orchard-watchers employ this device. [15]
3 · Why does the air not become moist when it comes into contact with water? For all other things become moist when they touch water. Is it because the extremities of the air and water meet, but the surface of each remains distinct?4 All other things then are heavier, but the air does not sink below the outer extremity of [20] the water. It therefore touches it, because there is nothing between them; but it does not become wet, because it always remains above the water.
4 · Why does calm weather occur most often at midnight and at midday? Is it because calm is immobility of the air, and the air is most at rest when it either has [25] the mastery or is overmastered, and it is in movement when it is struggling? Now it has the mastery most at midnight and is overmastered at midday; for at the former time the sun is farthest away and at the latter nearest at hand. Again, the winds begin to blow either about dawn or about sunset; and the wind which blows at dawn dies down when it is overpowered, and that which blows at sunset dies down when it [30] ceases to have the mastery. Consequently the former dies down at midday, the latter at midnight.
5 · Why is it colder when dawn is breaking and it is already early morning than at night, although the sun is nearer to us? Is it because towards daybreak dew and hoar-frost fall, and both of these are cold? The whole ground then being as it [35] were sprinkled with cold moisture, a process of cooling takes place.
6 · Why is it that in Pontus both intense cold and stifling heat occur? Is it because of the thickness of the air? For in the winter it cannot be thoroughly warmed, and in the summer, when it is heated, it burns because it is thick. It is for [938b1] the same reason also that marshy regions are cold in winter and hot in summer. Or is it because of the course of the sun? For in the winter it is far away, and in the summer near at hand.
[5] 7 · Why is the sky finer at night than by day? Is the sun the cause of wind and disturbance? For these occur when some movement takes place; the cause therefore is the heat. So, when the heat is not present, everything is at rest, and there is more rest when the sun is rising than when it is sinking. And the saying,
[10] Having no fear of a cloud from the land,
means that, where there is most movement, there must be least permanence and consistency, that which is trying to hold together being irregular and unable to gain the mastery. And this is what happens on the sea in winter and on land in summer.
8 · Why is it that when liquid which fills a jar is poured into skins the jar not [15] only holds the liquid and the skins as well but also has room for more liquid? Is it because there is air present in the liquid? This then, when it is in the jar, cannot be given off owing to the size of the jar; for the larger anything is the more difficult it is to press any moisture or air out of it, as can be seen in sponges. But when it is divided [20] up into small portions, it is pressed out of the skin together with the air already there, so that the space occupied by the air becomes empty; and so the jar can hold the skins and additional liquid as well. This is more especially the case with wine, because there is more air in wine than in water. Similarly the same vessel can hold [25] the same quantities of ashes and water together as it can hold of each poured in separately. For there are apparently many empty spaces in ashes, and so the water, being thinner, sinks in more and saturates the ashes, so that they become dense, because the saturation takes place in one part after another (for a thing always becomes more thoroughly saturated if the process takes place little by little than all [30] at once), and, as this takes place, the ashes gradually sink, at the same time absorbing the liquid because they contain hollows. (But ashes thrown into water while still hot cleave the water and cause it to evaporate.) And the same thing happens if the water is poured in first and the ashes put in afterwards, so that the [35] water also would seem to contain hollows and empty spaces. Or do the ashes take up the water, and not the water the ashes? For it is only natural that that which is compose
d of smaller particles should be that which finds its way into something else. (Further, this can be illustrated by an experiment; for when ashes are sprinkled water is attracted to any spot where they are sprinkled; whereas the contrary would [939a1] have taken place if it were the water which takes up the ashes.) Or does this process not occur if the water be poured in first and fill the vessel to the brim, but, if anything then be added, does it overflow? But if the water once overflows and the ashes settle down, then it does occur; for it was the ashes which took up the water. [5] There is a parallel to this in the fact that trenches do not hold all the earth which has been dug out of them; for apparently some air occupies the space excavated, and for this reason it does not hold all the earth.
9 · Why is it that, though air is denser than light, it can pass through solids? [10] Is it because light travels in a straight line only, and so the sight cannot see through porous substances like pumice-stone, in which the pores are irregular, whereas they are not so in glass? The air, on the other hand, is not obstructed, because it does not travel in a straight line through anything through which it passes. [15]
10 · Why is it that the air becomes cold by touching water but not moist, even though one blows so hard upon water as to cause waves? That it becomes cold is clear from the change which it undergoes; for the air from water causes cold. Is it because it is the nature of air to be cold or hot, and it changes by touching anything [20] with which it comes into contact; but it does not also become moist, because it is too light and so never penetrates below the level of the water, but always remains in contact only with the surface, even though it be forced downwards, and the water then recedes still lower, so that the air can never penetrate into its depth?