The male differs from the female in that the former is hotter and drier; the latter is, on the contrary, colder and moister.

¶ Here begins the treatise on non-natural things.

And first on the change of air.

A large ornamental woodcut initial 'A' features intricate foliate and scrollwork designs.

The change of air happens in five ways: either it happens from the seasons of the year, and from the rising and setting of the stars, from the winds, from the lands, and from their vapors.

¶ On the seasons of the year.

The seasons of the year are four: namely, spring, which is temperate, hot, and moist; summer, which is hot and dry; autumn, which is cold and dry; and winter, which is cold and moist. The nature of the air is changed by the stars. For when the sun approaches the stars, or they approach it, the air becomes hotter. When these are separated from each other, the coldness of the air changes: namely, it either increases or decreases.

¶ On the number of winds and their qualities.

There are four winds: namely, the subsolanus east wind, the favonius west wind, the septentrio north wind, and the auster south wind. One of these has a cold and dry quality. Another has a hot and moist quality. The other two, however, are of equal quality. To the one, namely the subsolanus, heat and dryness are attributed. To the other, the favonius, coldness and moisture are attributed. And the auster is a little hotter and moister. The septentrio is colder and drier.

¶ On the modes of lands and their qualities.

The modes of lands are four: altitude, depth, proximity to mountains and the sea, and the equality of the lands or places by which lands differ from one another. Regarding altitude and depth: altitude causes coldness, and depth renders the opposite. Proximity to mountains brings about these effects: for if they are on the southern side, the land will be cold. For the mountains obstruct the hot southern winds, and the northern winds strike it with cold blasts. If, however, the mountains are to the north, it will be the opposite for the land above. Regarding proximity to the sea: the south makes the land hot and dry, while the north makes it cold and dry. Furthermore, lands differ among themselves by their nature. For if the land is stony, it is cold and dry. If it is rich and thick, it is hot and moist. Clay, however, is cold and moist. The air is also changed by the vapor of marshes or any rot, from which diseases and plagues occur in humans.

¶ On the exercise of the body.

Exercise changes the body. Because when it is balanced, it provides balanced heat. When it becomes greater, it heats more, but afterwards, it cools and dries. The body is changed by idleness because, if it is unequal, it causes coldness and an unequal moistening; if it is equal, it does so equally.

¶ On the division of the bath.

The water of the bath is either sweet or not sweet. Sweet water in a bath softens; hot water heats, and cold water cools. A bath of water that is not sweet dries the body. If it is from salty, bitter, or sulfurous water, it heats and dries. If it is aluminous and gypseous containing gypsum/chalk, it cools and dries.