of their appearance by day is that the sun’s light is stronger then, and the atmosphere itself when stirred and warmed by it is less dense.
The moon’s power, on the other hand, is feebler, and is therefore more easily resisted by the surrounding air. The rest of the heavenly 11 bodies are equally weak, and unable by their own force to burst through the atmosphere. So their shape is impressed and retained in the more solid and less yielding medium. For, in order to produce the phenomenon, the atmosphere must neither be so thick as to exclude or dissipate the light that streams in on it, nor yet so thin and rare as to furnish no hold to the rays that fall upon it. This particular consistency is obtained at night: the sluggish air is at that time struck with the faint light from moon or stars without violence or rudeness, and, being thicker than it is wont to be by day, is tinged thereby.
III On the contrary, _the Rainbow_ does not occur by night, except on 1 very rare occasions, inasmuch as the moon has not sufficient strength to pierce the clouds and suffuse them with hues such as they receive from the brilliant light of the sun. The shape and varied colours of the rainbow are due to the peculiarities of different kinds of clouds.
Some parts of the clouds are swollen, others hollow; some are too dense to transmit sunlight, others too rare to exclude it. This difference in 2 consistency causes alternations of light and shade, and produces that marvellous variety presented by the rainbow. Another explanation is offered in instances like the following: When a pipe bursts anywhere, the water is observed to be forced by pressure through the small opening; the drops seen against a slanting sun reproduce the appearance of the rainbow. Again, if you will at any time watch a fuller at work, you will observe the same appearance: when he has filled his mouth with water and spirts it lightly on the clothes stretched on pegs, the air thus besprinkled exhibits plainly the various colours that shine in the bow. One cannot doubt that the reason of this lies in the moisture. 3 For a rainbow never occurs except when there are clouds about.
Let us inquire how it is produced. Some authorities say that there are certain drops of water that transmit light, while some are too compact to be translucent. Thus the brightness is the effect of the former; the shadow, of the latter; by the intermingling of the two is formed the rainbow, part of which is bright, to wit, that which admits sunlight, part darker, namely, that which has shut out the light and cast a shadow from itself over the objects nearest it. Others again deny that 4 this is so. Shade and light, they say, might be the cause if the rainbow had only two colours, and thus was made up of light and shade.
But now, though there gleam a thousand diverse hues, Their changes withal elude the eyes that behold.
The hues that touch seem actually one, yet the edges are quite different.
In it sight detects something that is red, something that is orange, something that is blue; and there are other colours too, laid on in finest lines just like a skilful painting, so that, as the poet remarks above, it is impossible to discover whether the colours differ from one another until the last of them is compared with the first. The junction 5 of colour with colour deceives the sight: with such marvellous skill does nature starting from what is like end in what is totally unlike.
What good, then, do the two alleged colours, light and shade, do in a case of this kind, when the presence of an endless variety must be accounted for? Again, certain authorities are of opinion that the following is the method of formation of the rainbow: In the quarter of the sky where rain is falling, they say, the drops of falling rain are so many mirrors; from each mirror, therefore, is reflected an image of the sun. By and by, many, in fact, countless, images, descending and crossing abruptly, are all blended together. Therefore the rainbow is just a blending of a great number of images of the sun. They appeal to the following argument in proof of this: On a clear day, say they, 6 set out a thousand basins, and they will all contain images of the sun.
Or arrange single drops of water on single leaves; they will each have an image of the sun. On the other hand, an immense pond will have no more than one image. Why so? Just because every smooth surface that is fenced off, and surrounded by its own boundaries, is a mirror. Again, divide a pond of very large size into several small ponds by inserting partition walls; it will show as many images of the sun as it has divisions. Leave it as it was, spreading out to its full extent, and it will show but one reflection of him. The small extent of the liquid or 7 pond makes no manner of difference. If the surface is circumscribed, it forms a mirror. Well then, those countless drops, which are carried down by a falling shower, are so many mirrors, and contain so many reflections of the sun. To an observer right in front of them they present the appearance of being mixed up: the intervals which part them from each other are not distinguished, their mere distance from the observer prevents discrimination of them. By and by instead of individual drops there is seen a single blurred mass that contains them all.
Aristotle agrees with this opinion. His words are: Beams of light are reflected by sight from every smooth surface. Now, nothing is 8 smoother than water and air. Therefore, our sight is reflected back on us from thick air. Indeed, where the vision is dull and feeble, the slightest stroke of air checks it. Some people suffer from an affection which causes them to think that they are meeting their own image, and they see everywhere the reflection of themselves. And why? Because the power of their eyes is so weak that it cannot overcome the resistance of even the nearest layer of the atmosphere. What dense air effects in ordinary cases, any kind of air is sufficient to effect in the cases referred to by Aristotle. For whatever the nature of the air, it is strong enough to defeat weak sight. Now, much more is our vision reflected upon us by water because it is denser and cannot be pierced; it absolutely stops the rays from our eyes, and turns them back to the source whence they proceeded. Well then, when there are numerous 9 raindrops, they are just so many mirrors. But on account of their smallness they express the sun’s colour without distinct shape. By and by when the same colour is reflected in the countless drops that fall without intermission, it begins to take on the appearance not of numerous images with intervals between, but of a single, long, uninterrupted image.
But how, you may object, can you tell me that there are many thousands of images there, where I can see none at all? Besides, as there is but one colour in the sun, why are there different colours in the 10 reflections of him? These objections which you have put forward, as well as others that no less call for refutation, I will endeavour to refute. And let me say, first of all, that nothing is more deceptive than our eyesight, not merely in objects whose careful examination is prevented by distance in position,[26] but even in objects seen close at hand. An oar, though quite whole, presents the appearance of being broken when seen in clear shallow water. Apples seen through glass appear much larger than they really are. In long colonnades, pillars 11 set at intervals present an apparently unbroken continuity of line. Or go back to the case of the sun himself; his orb, which reason proves to be larger than the whole earth, is so contracted by human sight that some of the philosophers have maintained that it is only a foot in diameter. He is, we know, the swiftest of all luminaries, yet none of us can see him move; nor should we believe that he does advance, were it not evident from time to time that he has advanced. The world itself glides on with headlong speed; within an instant of time it unfolds its risings and its settings, yet none of us is aware of its movement. What cause, then, is there for wonder if our eyesight cannot separate 12 the drops of the rain showers, and loses the distinction of the images on account of the vast distance at which they are beheld? At any rate no one can doubt this, that the rainbow is a reflection of the sun, formed in a hollow cloud full of moisture. This is made plain from the simple fact that the image is never seen except opposite the sun, high up or low down, in inverse relation, just as he sinks or elevates his course. When he descends, it is higher; when he is high in the heavens, it is more sunken. A cloud of the required kind is often at the side 13 of the sun without producing a rainbow, because it does not catch his image straight in front.
[26] The received text gives “diversity of colours.”
As to the variegation in colour, it is due simply to its double source, derived partly from the sun, partly from the moist cloud. The moisture produces lines now blue, now green, now purple-like, and orange or red--the two shades, dull and bright, combining to produce this diversity. So also, a purple garment does not always come out 14 in exactly the same tint from the same dye. Differences depend upon the length of time it has been steeped, the consistency and the amount of moisture in the dye it has imbibed: it may be dipped and boiled more than once, or it may have received only one immersion. In like manner then, when there are the two elements, sun and cloud, in other words, object and mirror, it is little wonder that as many varieties of colour are generated as can be produced from them in higher or lower tone in countless different categories. For example, there is one 15 colour that proceeds from the light of fire, another from a light that is duller and less violent than fire. In other details concerning the rainbow the method of inquiry is full of uncertainty; there is nothing concrete to lay hold upon, and conjecture must be ventured in every direction. But in this question of its origin doubt is precluded; for it is evident that the causes of the rainbow are two in number, sun and cloud. The bow never appears when the sky is clear, and never when it is so cloudy as to hide the sun. It must, therefore, unquestionably arise from these, failing either of which it cannot come into being.
IV A further consideration must be mentioned, which is just as manifest 1 as the preceding, to prove that the reflection is given back after the fashion of a mirror; it is never given back save from straight opposite to the sun, that is,[27] unless on one side stands the object to be reflected, and on the other the mirror that reveals it. Proofs are adduced by the mathematicians that are not merely convincing but that compel belief of this. Nor can doubt be left in any mind that the rainbow is an image of the sun, imperfectly reflected owing to the defective shape of the mirror. But meantime let us recall other proofs that may, so to speak, be picked up in the street without any 2 reference to mathematics. Among the proofs of this origin of the bow I place the extreme rapidity of its emergence. In a single moment the huge form with its thousand lines is inwoven in the texture of the heavens, and just as rapidly does it fade. Now, nothing is returned so quickly as an image from a mirror. The mirror does not create anything, it merely reveals it. Artemidorus of Parium tells us further even the kind of cloud required to reflect such an image of the sun. If you 3 make a concave mirror, he says, that is, one resembling half of a ball cut through the middle, and take your stand outside the centre, then those who stand beside you will appear in the reflection inverted and nearer to you than to the mirror. The very same thing, according to him, takes place when we look at a round hollow cloud from the side: 4 the image of the sun detaches itself from the cloud, and is nearer us and more turned in our direction. Therefore the red colour is from the sun, the dark blue is from the cloud: the other hues are produced by a blending of these two.
[27] In a writer less prone to repetition the words to the end of the sentence would seem the insertion of a copyist.
V But there are arguments on the other side. About mirrors there are 1 two opinions; some people think that only phantoms are seen in them; in other words, the shape of our bodies, an emanation separated from our bodies. Others, however, affirm that images do not exist in the mirror, but that it is the very bodies that are seen, the eyesight being bent back and reflected on itself again. Now, the point is not how do we see whatever it is we see: the question is, how the image should resemble the original in the cloud as in a mirror.[28] Could anything be more 2 unlike than the sun and a rainbow in which neither the colour nor the shape nor the size of the sun is to be seen? A bow is far larger and, in the bright part, far redder than the sun: in the other colours, too, it is different from him. Besides, when you insist on comparing a mirror to the atmosphere (_i.e._ as embodied in a cloud), you must show me in the latter the same smoothness of texture, the same levelness of surface, the same brightness as in the former. But surely no clouds resemble mirrors to this extent. We often pass through the middle of clouds without seeing ourselves in them. People who climb to the tops of mountains look down on cloud, but cannot make out their reflection 3 in it. True enough, but it is separate drops that are separate mirrors, says my opponent. Admitted. Still, I deny that a cloud consists of fully formed drops. It no doubt contains the elements from which the drops are formed, but not as drops. Clouds do not contain even water, but only the material to form water. Granting, for the sake of argument, that there _are_ countless drops in the clouds and that they can reflect an object, yet they do not all produce one and the same reflection, but each its own. Further, you may join mirrors to one another, but they will not unite to form a single reflection: 4 each portion will enclose a likeness of the object. Some mirrors are composed of a large number of very small parts. Set before them one man and a whole people is reflected, each portion producing an image of its own. The portions of the mirror thus united and placed side by side none the less keep their images separate, and out of one man make a crowd. But they do not blend in one that troop; 5 they separate and distinguish the individual faces. Now, a rainbow is bounded by a single outline, the whole presents but one representation.
[28] The reading of the MSS. is admittedly corrupt. I have followed Ruhkopf’s conjecture, though without conviction. The argument seems instead of _similis_ = like (“resemble” in the text): in that case the meaning would be: how an image unlike the original ought to be reflected from the cloud as from a mirror. Cf. § 13 below.
Well, but, says our opponent, is not the water that is scattered from a burst pipe, or that is tossed up by the oar, wont to exhibit something similar to these colours that are seen in the bow? True, but not for the reason which you wish to bring out, to wit, that each single droplet receives an image of the sun. As a matter of fact, the 6 drops fall too quickly to be able to form such an image. The medium must be stationary in order to receive the impression of what is to be reproduced.
How, then, it may be asked, does it come about? The drops, I reply, receive the colour, but not the image of the sun. Besides, as Nero Caesar says very elegantly: The neck of Venus’ dove glitters as the bird tosses its head, and so the neck of the peacock shines with varied colours as often as it is turned hither and thither. Are we, therefore, to say that feathers of this kind, whose every turn passes into new colours, are 7 mirrors? Well, clouds differ in character from mirrors no less than the birds mentioned, and as chameleons and the other animals whose colour changes. In the latter case the cause is sometimes subjective: the creatures when inflamed with anger or passion vary their hue through the suffusion of moisture: at other times the position of the light, direct or slanting, gives the colour its particular hue. What resemblance, I say, is there between mirrors and clouds? Whereas 8 those are not translucent, these transmit light. Those are dense and compact, these are rare. Mirrors are of uniform material throughout, clouds are made up of various elements brought together at random, and therefore are full of internal strife, and cannot long hold together.
Consider further; at sunrise one sees a certain portion of the sky ruddy; at other times one sees clouds of fiery red. This particular colour is received by the clouds from encountering the sun: what, then, is there to prevent the many colours of the bow being derived by them in the same way from him, even though they do not possess the power of mirrors? A little ago, my opponent retorts, you advanced the argument 9 that the rainbow is always produced opposite the sun, because an image could not be reflected from a mirror unless the object were in front of it. We agree in this point, he adds. Yes, for just as the object whose image is to be transferred to the mirror must be set opposite the mirror, in like manner, in order that the clouds may be tinged by the sun’s rays, the sun must occupy a suitable position. He does not produce the same effect if his light streams in on all sides; there must be a proper incidence of the rays to produce the effect. Such are the reasons alleged by those who will have it that the rainbow is a coloured cloud.
Posidonius and those who are of opinion that the phenomenon is produced by reflection as from a mirror, answer their arguments thus: If there 10 were any real colour in a bow, it would persist, and be seen more distinctly, the nearer it is. As it is, the image of the bow is clear only in the distance; it is lost as it begins to approach. I do not agree with this argument in refutation, though I approve the main sentiment which it supports. And I will tell you why. The cloud _is_ coloured, but in such a way that the colour cannot be seen from every point. And no more can the cloud itself: for no one who is in it can see it. What wonder, then, if its colour cannot be seen by one 11 to whom itself is not visible? And yet, although the cloud is not seen, it is there: and so is the colour. It is, therefore, no proof of the deceptiveness of the colour that it ceases to be manifest when one approaches it. For, I repeat, the same happens to the clouds themselves: they are not all a sham merely because under certain conditions they cease to be visible. Besides, when you are told that the cloud is dyed by the sun, it does not mean that that colour of his is mingled, as it were, with a hard, firm, durable body, but with a liquid unstable body that is incapable of more than a very brief impress. Let me add that there are certain artificial colours which 12 display their virtue at a distance. The better and richer the Tyrian purple is, the higher up you must hold it to display its full blaze. It does not cease to possess its colour simply because it does not reveal its best shade in any and every position in which it is exhibited. I am of the same opinion as Posidonius in holding that the bow is formed in a cloud shaped like a hollow round mirror, whose form is that of a section through a ball. This cannot be proved without the aid of 13 geometry: the mathematical proofs leave no doubt that the bow is an image of the sun, but one that does not resemble it. Nor, indeed, are all objects faithfully represented in mirrors. There are some mirrors one is terrified to let one’s eyes rest upon, such is the misshapen and distorted image they reproduce of those who gaze upon them. They deform the likeness they preserve withal. Some, again, there are, a glance at which causes great self-satisfaction in one’s strength: the arms are 14 enormously increased, and the appearance of the whole body is enlarged to superhuman proportions. There are mirrors that turn faces to the right, and mirrors that turn them to the left, others twist and even invert them. What wonder, then, that a mirror of this kind should be formed in a cloud by which a defective appearance of the sun should be presented?
VI Among the other arguments it must be mentioned that a rainbow never 1 is seen greater than a semicircle: the higher the sun is, too, the smaller is the bow. As our countryman Virgil says: And deep drinks The mighty bow, when rain is brewing. But the threat the bow conveys is not the same whatever the quarter it has shown itself in. If it rises toward the 2 south, it will bring a heavy fall. The rain in that quarter, such is its force, cannot be mastered by the strongest midday sun. If it shine toward the west, there will be only a dew or a light rain. If it rise in the east or thereabouts, it prognosticates fine weather.
If, however, the bow is the sun’s reflection, why does it appear of far larger size than the sun himself? Just because there is a kind of mirror that exhibits objects on a far larger scale than that on which they are presented to it, increasing their form to a portentous magnitude: and in turn there is another kind that reduces the size. And tell me this again, why does an image assume the form of a circle if it does not answer to a circle? You may, perhaps, tell me why the colour 3 of the bow is varied: why its shape is what it is, you will not be able to tell me except by citing some model after which it is formed. Now, other model there is none save that of the sun; when you admit that the rainbow receives its colour from him, it follows that it receives its shape also from him. In short, you and I are agreed that those colours by which its quarter of the heaven is adorned proceed from the sun.
But on one point we are not agreed: you say that the colour is real; I maintain that it is only apparent. Whichever it is, real or apparent, it comes from the sun. On your assumption its sudden cessation cannot be explained, seeing that all other bright lights in the sky are dispelled gradually. Its sudden appearance and, at the same time, its 4 sudden extinction make for my contention. For it is a peculiarity of a mirror that the reflection in it is not built up piecemeal, but all at once comes fully into being. Every image in it is destroyed, too, with as great rapidity as it was formed. For to the construction or removal of the images nothing is required but the presentation and withdrawal of the objects.
In the rainbow-cloud whose nature is in question, there is no proper substance or material: there is only a sham and a likeness without reality. Will you be convinced that this is so? The proof is, the 5 rainbow will cease if you conceal the sun. Place another cloud, I repeat, in front of the sun, and all the bright hues of the bow are gone. But what is to be said, you may ask, in explanation of the size of the bow which is considerably greater than that of the sun? I have already said that there are certain mirrors that multiply every object they reflect. I may now add that every object much exceeds its natural size when seen through water. Letters, however small and dim, are comparatively large and distinct when seen through a glass globe filled with water. Apples floating in a glass vessel seem more beautiful than they are in reality. The stars appear bigger if seen through a cloud, 6 because our vision is blurred in the moisture, and cannot accurately grasp its object. This will become plain to demonstration if you fill a cup with water and throw a ring into it. While the ring lies right at the bottom its appearance is visible on the surface of the water.
Anything, in fact, that is: seen through moisture appears far larger than. in reality it is. What wonder that the image of the sun, being 7 seen in a moist cloud, should be reproduced on a scale larger than the original, and that for the two reasons indicated? The cloud contains the two elements, one like glass, which can transmit light, and one also of the character of water; at any rate, if it does not just yet contain the actual water, it is now forming it, its nature is already such as can easily be changed into water.
VII As you have mentioned glass, some one interposes, I can draw from 1 this same material an argument to confute you. Glass sticks are manufactured, either fluted or bulging,[29] with many corners like a club. If one of these sticks is placed obliquely in the path of the sun’s rays, it sends back the colour which is wont to be seen in the rainbow. This proves that there is not here an image of the sun, but an imitation of his colour from reflection. Now, in this argument there are many points that make for my view. First of all, it is plain that 2 there must be some smooth surface like a mirror to reflect the sun.
Secondly, it is plain that no colour is formed in the rod, but only a false appearance of colour, such as I mentioned above, which the neck of a pigeon, as it is bent hither and thither, alternately puts on and off. This, I say, is seen likewise in the case of a mirror, which assumes no real colour, but only a certain imitation of the colour of a foreign body.
[29] Another reading gives “twisted.”
Still, this one point requires explanation; it is not the sun’s 3 image that is beheld in that glass stick, because it is not capable of expressing it accurately. True enough it tries to reproduce the image, because the material is smooth and suitable for this purpose. But it fails because its shape is unsymmetrical. If it had been suitably constructed, it would reflect as many images of the sun as it had faces. But since the sides are not distinctly separated from each other, and not bright enough to serve as mirrors, the images are only incipient, not fully expressed; they get confused through being crowded together, and are reduced to the appearance of a single band of colour.
VIII But to return--why does the bow not complete the full circle in its 1 form, but appear as only a semicircle when stretched to the full extent of its greatest span? Some are of opinion that the reason is that the sun, being much higher than the clouds, strikes them only on the upper side. Hence their lower parts are not touched by his light. Receiving the sun only on one side, the clouds reproduce only one portion of him, and this is never more than a half. There is very little force in this contention. My reason for saying so? The sun, even though he is on 2 the upper side, yet strikes, and therefore colours, the whole cloud.
How could it be otherwise? His rays are wont to be transmitted through the clouds and to penetrate any density in them. Further, the proof they advance is flatly in opposition to their main proposition. For if the sun is higher than the clouds, and his beams, therefore, shed only on their upper side, the bow would never come down as far as the earth.
Yet it does descend to the very ground. Besides, the bow is never 3 seen except opposite to, not below, the sun. The fact is, the sun’s highness or lowness does not affect the matter: the side of the cloud that faces him is struck by him throughout its whole extent.
Furthermore, sometimes even the setting sun produces a rainbow; surely at that time, being near[30] the earth, he strikes the clouds on their lower side. And yet then, too, the bow is only a semicircle, though the clouds receive the sunlight on their lower and darker portions.
The Stoics, who hold that the light is reflected in the cloud as 4 in a mirror, make the cloud hollow like the section of a ball. Such a mirror, being but part of a circle, cannot, they think, reproduce a whole circle. I give my adherence to the proposition, but I cannot agree to the argument in its support. For, if the whole figure of a circle placed opposite a concave mirror is reproduced in it, then there can surely be nothing to prevent the whole of a ball being seen in a semicircular circular mirror. Besides, we have already shown that 5 complete rings resembling a rainbow surround the sun and the moon at times. Why should the circle be complete in the halo, but never in the rainbow? And then again, why should the clouds that receive the sunlight be always hollow ones, and not sometimes flat or bulging?
[30] The common reading makes this adjective refer to clouds--the clouds which are near the earth.
Aristotle says that rainbows are formed, after the autumnal equinox, at any hour of the day, but in summer only either in the early part of the day, or when the sun has begun to sink. The cause of this is obvious. In the first place, about midday the great heat of the sun 6 dispels the clouds: he cannot be reflected in the clouds which he breaks up. But in the early morning and as he sinks toward the west, his rays have less power, and can thus be resisted and reflected by the clouds. In the second place, the sun is not wont to form a bow except when he faces the clouds in which it is formed. When the days are 7 shortening in autumn, his rays are always slanting. Therefore, he has some clouds facing him that he can strike, at any part of the day, even at the hour at which he attains his meridian height. But in the summer season he sails right overhead. Therefore, in the great altitude of his midday course, he looks down on the earth too directly to encounter any clouds. He has them at that period all beneath him.
IX I must now go on to speak of _Streaks_ (watergalls, sun-dogs), which 1 are as bright and varied as the rainbow, and commonly received by us as equally indicative of rain. No great labour need be spent in explaining them, for they are just incomplete rainbows. They have the variegated 2 appearance of the bow, but none of its curve. They lie in a straight line. They are formed near the sun, as a rule, in a moist cloud that has begun to break up. Thus, they have the same colour as is found in the rainbow, but there is a difference in the shape, due to the corresponding difference in the clouds over which they stretch.
X There is a similar variety of colours in _Halos_. But there is this difference in the various phenomena: Halos are formed at any point in the sky, wherever there is a heavenly body; rainbows are not found except opposite the sun; streaks, only in the neighbourhood of the sun.
I may express their difference in another way: Bisect a halo and you have a rainbow; make it a straight line and you have a streak. In all three there is the same multiplicity of colours, the scale running from dark blue to orange. Streaks, then, are found only close to the sun.
Rainbows are all either solar or lunar. Halos are seen with all the heavenly bodies.
XI Another kind of streak is visible when thin rays of bright light 1 equidistant from one another are shot out through narrow apertures in the clouds. These, too, are a prognostication of rain. How am I to express myself here? What shall I call them? Images of the sun?
The chroniclers call them merely suns, and have put on record that they have been seen in twos and threes. The Greeks call them _Mock 2 Suns_ (parelia = beside the sun), because they are generally seen in proximity to the sun, and somewhat resemble the sun. They do not give a complete reproduction of the sun, but exhibit only his size and shape.
They are dull, however, and languid without any of his heat. What name are we to apply to them? Shall I do as Virgil did---hesitating about the name, employ the very name which causes the hesitation?
And by what name[31] shall I call you, Rhaetian wine?
But yet you must not seek to compete with the Falernian bins.
[31] He has altered Virgil’s word “carmine” to “nomine” to suit his meaning, or, as the editors say, _lapsu memoriae_.
There is no objection to my calling these, mock suns. They are, in fact, images of the sun formed in a thick cloud close to him after 3 the fashion of a mirror. Some writers define a mock sun as a cloud, round, bright, and resembling the sun. The mock sun follows the sun, and is never left farther behind him in his orbit than it was at its first appearance. None of us, I suppose, is surprised at seeing a reflection of the sun in some fountain or quiet lake. Well, his disc may be reflected in the heavens just as readily as on earth, if only the material is suitable to produce the reflection.
XII Whenever we wish to observe an eclipse of the sun, we place on the 1 ground basins filled with oil or pitch. The thick liquid is not easily disturbed, and therefore retains the images it receives. Images, I may observe, cannot be seen except in a liquid at rest. Then we are in the habit of noting how the moon obstructs the sun, and by the interposition of her body hides his, which is so much larger, sometimes partially, if it so fall out that she only encounter a portion of his orb, sometimes completely. The latter is called a total eclipse: it quite shuts out the light and shows us the stars; it occurs when the 2 centre of the two bodies lies in the same straight line. Now, just as the image of both sun and moon can be seen on earth, so it is in the case of mock suns in the atmosphere. The still air is so compact and yet clear that it can receive the sun’s likeness. Other clouds receive it, but let it go if they are either in motion, or thin, or black. The moving clouds disperse it, the rare let it slip, the black and impure do not take the impress of it, just as on earth soiled objects do not reflect an image.
XIII Mock suns are wont to be formed in pairs and on the same principle. 1 There is nothing, in fact, to prevent the formation of as many as there are clouds suitable for exhibiting an image of the sun. Some writers are inclined to hold that when two such phantoms are visible, one arises directly from the sun, the other from his image. For, to use an illustration from common experience, when several mirrors are so arranged that one is in sight of the other, all reflect the same image; but only one is directly from the original, the rest are reflections of images. The nature of the object presented to the mirror makes 2 no difference in the effect. Whatever it sees it reproduces. So, up on high there, if some chance has so disposed the clouds that they face one another, one of them reflects the image of the sun, the other the image of his image. The clouds that produce this effect must be dense, smooth, bright and flat, analogous in character to the sun. All