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 phantoms of this kind are white and resemble so many discs of the moon, for the reason that the sun’s light that they receive and reflect back is always oblique. If the cloud, on the contrary, is beneath the 3 sun and too near him, his rays dispel it: or again, if situated too far away, it does not reflect them nor produce any image. In ordinary experience in the same way mirrors withdrawn to a distance from us do not reproduce our features because our sight cannot carry back to us from them. These suns, too--to employ the name given by the chroniclers,--are an indication of rain, especially if they have their position in a southern quarter, from which the most heavily-charged clouds chiefly come up. When such an image surrounds the sun on both sides, then, if we are to believe Aratus, a storm is brewing. XIV