It is said that the moon does not decrease or grow, but, being illuminated by the sun on one side and gradually moving away from it, then approaching it, turns to us now with the light side, now with the dark side. On the day of the new moon, when the moon begins to rise, we see it lying on its back face up, because it is above the sun [and illuminated] from below; at this time it sinks to the north; during waning, it stands vertically and inclines to the south; the full moon is always opposite the sun. The moon is always [standing] high when the sun is low, and low when the sun is high, and [the luminous part of it] increases from the second day... until it becomes full, and then it decreases, after which it is not visible for 13 parts, [i.e., degrees], because of the sun. The young Moon always appears, whether at night or during the day, in the constellation of Aries. If, when rising, it was located vertically, then, when rising in the morning, it will seem to face upwards. If, on the contrary, when it rises, it seems to be turned upwards like a ship, then in the morning at sunrise it will be seen in an upright position. Thus, it has three positions and can be seen sometimes turned up, sometimes downward, sometimes standing upright.

Chapter 25. About air

Air is everything that, being like emptiness, exudes a life-giving spirit, in which birds and clouds fly and storms [rush by]. Here also the air forces, overthrown from the highest throne, are tormented by the expectation of the day of judgment, when they will be most severely condemned. Appearing to people, they dress aerial bodies corresponding to the dignity of each. And over the Moon, whose orbit serves as the boundary between air and ether, purity and eternal light reign, and it is said that not far from here is the vership of Olympus. But we see the stars in the darkness at night, the reflections [of this light]. The upper and clear air belongs to heaven, and the lower air, which becomes coarse and corporeal from moist vapors, belongs to the earth: for it is here that fire, hail, snow, ice, and thunderstorms are commanded, which are commanded to praise the Lord on earth. But sometimes this [earthly] air is also called heaven: for example, Peter says that the heavens perished during the flood, because the air was tossed up by the whirlwinds, swirling into whirlpools of waves. And the heavens of heavens are called the starry heavens — [in contrast to] these airy heavens, as higher than the lower.

Chapter 26. About the winds

Wind is the air set in motion, as can be easily seen with a small fan. And it is explained only as a stream of air, which, according to Clement, rushes down from some of the highest mountains, compressed and constrained, according to divine determination; [this stream] forms the winds, which are supposed to agitate the sea and soften the heat. The winds received different names in different parts of the sky. [149]

Chapter 28. About thunder

It is said that thunder comes from the rupture of clouds: the winds, once within them, turn there from side to side due to the mobility of their nature, seeking everywhere a way out and trying to break out; when they break free, they make a terrible noise and crack, like four horses jumping out of a stable, or a bubble, which, although small, makes a very loud sound when it bursts.

Chapter 29. About Lightning

Lightning is born from the friction of clouds, as [sparks] are born from the collision of stones, and after them comes thunder, but the sound reaches the ears later, than the brilliance reaches the eyes. After all, the collision of any objects causes fire. However, some say that the lower layers of the air contain water due to evaporation, and the upper layers contain fire due to the heat, and whenever they collide with each other, there is a terrifying crash of thunder. And if the fire wins at the same time, then there will be no harvest, but if there is water, then there will be abundance. And the fire of lightning has greater power [in comparison with earthly fire] because it consists of finer elements than that which we use.

Chapter 30. When they don't happen and why

In winter and summer, lightning is rare, as the frosty air extinguishes all the fire that falls into it. In hot summers, vapors rarely condense into clouds, and even then into rarefied ones, and without dense clouds there is no lightning. It is this circumstance that protects Scythia [22] and Egypt from lightning, while Italy is subject to them in the highest degree, because, on account of the mild winters and rainy summers, spring and autumn seem to reign there all the time.

Chapter 31. About the rainbow

A four-coloured rainbow in the air is formed by the sun and the clouds opposite it: a ray of sunlight falling into a hollow cloud is reflected and refracted into the sun, just as the pattern of a ring is reproduced on wax; At the same time, he [the ray] borrows the fiery color from the sky, purple from the waters, hyacinth from the air, and grass from the earth. [A rainbow] is less frequent in summer than in winter, and rarely at night, except at a full moon, when it reflects the moonlight.

Chapter 32. About clouds