The north wind comes to us from high and frozen places and therefore can draw no moisture from them; and so it is pure and clean, because it is cold and dry; and for this reason it is in itself very light, but its velocity makes it powerful in its impacts. The south wind does not blow pure and, because it is warm and dry, it dissolves the thickness of the watery vapor that exhales from the Mediterranean sea. These vapors then follow the course of the said wind, because they mingle with it; whence for this cause that wind, when it strikes Europe, comes to be warm and humid and of thick nature and, although its motion is sluggish, its impact is no less powerful than the north wind. Every wind is by nature cold and dry, but it takes on as many various dispositions as the places it passes through are various, leaving in its passage its humidity and coldness in dry and warm places, and then taking dryness and warmth from warm and dry places; and so in its motion it changes into various compressions in every region; and in becoming warm and dry it weakens in its power, and in taking up again the things it had left, it takes up with them the said forces, because at equal velocities of motion that thing gives the greater impact which is of greater heaviness, and conversely the lighter gives a lesser impact. When the sun returns in summer to the parts of Africa, the moisture that had been multiplied there during winter comes to be dissolved and its quantity grows, and with fury it seeks places capable of its increase. And this is the south wind that in autumn drives before it the maritime Mediterranean vapors and condenses them over our regions. And they fall down again for want of support. When many winds fight together, then the waves of the sea have no free course, but strike together and rise up high and sometimes submerge ships; and in such contention the upper wind will be the victor, being subtle and less interwoven and mixed with the other winds.

When one thing is the cause of another, it induces by its movement some effect; and the movement of the effect must follow the movement of the cause. As if to say: the moving body joined with its mover follows the motion that the mover makes, and if the moving body separates from its mover, it follows the motion begun by that mover along the same line, but not with as much power, because in separating it becomes lighter. Every motion arises from excess or deficiency, or, I would say, from congregation or disgregation. The thing that moves follows the motion made by its mover. * The air that rises through heat, which draws to itself the moisture infused in it when it is with... Cold draws moisture and heat drives it off. See the vessel of water when it is heated, which makes that water convert into vapor and its quantity greatly increases; and if you leave a small vent in that vessel, you will see such vaporization breathe out through that place; and it will blow and run with impetus among the other air. Cold draws the moisture and the air follows it, and heat drives it off, and the air flees, pushed by the wave of the multiplied vapor, which seeks a place capable of its increase.