The elements convert one into another; and when air converts into water through the contact it has with its cold region, then it draws to itself with fury all the surrounding air, which with fury moves to fill the place vacated by the fled air, and so one quantity moves successively behind another until they have in part equalized the space from which that air separated: and this is the wind. But if water converts into air, then the air that first occupied the site where the said increase spreads must with flight and impetus give place to the newborn air: and this is the wind. Of simple motion. The moving body can never be swifter than its mover in an equal time. Therefore the wind moved by the stars does not have the velocity to circle the earth in 24 hours, as the star, its mover, would. Therefore such a saying is false. Albert. - The vapor of the wind is generated by heat and is struck and driven off by cold; which cold drives it before it, and where the heat is driven off it stays cold; whence the vapor that is driven off cannot return upward because of the cold that drives it down, and cannot return downward because of the heat that lifts it up, whence it must needs go crosswise. And for my part I judge that it has no motion, because the said powers, being equal, equally close upon their middle; and if indeed it flees, the fugitive exhales and flees in every direction, like a sponge full of water which, when squeezed, sends the water fleeing along every line from the center of that sponge. Therefore the north wind would be the generator of all the winds at one and the same time.

That heavy body will become lighter which occupies more air. And that light body will become heavier which is made of smaller figure. The transverse motion, drawn from the power of its mover, will never be straight. Although to someone it may seem that the motion of an arrow is for some space made in a straight line, this cannot be, but there will indeed be an imperceptible variation, which is not perceived by the sense of the eye. * It is proved. If the arrow, with one degree of natural weight [set] to go to the center of the world, and being at the start moved by transverse motion with a power of a thousand, acquires during that motion a power of a thousand. * It is proved. Let us say that the force of the mover attaches itself to the moving body with a power of a thousand, and that such power is consumed in a thousand degrees of motion. * It is proved. Let us say that the moving body of itself tends with one degree of power to descend to the center of the world, and that the power applied to that body by the mover in the transverse motion is a thousand degrees of force, and that the quantity of the motion is a thousand degrees of space. I say that the power applied to the moving body will lack one degree of force in one degree of space, and that the body will descend one thousandth of a degree of motion toward the center, which is imperceptible to the eye; for if the motion of the crossbow's arrow were 500 braccia, dividing those 500 braccia into a thousand degrees, each degree would be half a braccio, and the thousandth of a half-braccio is nearly imperceptible, being like a hair; and if the degrees of the motion and of the moving force were 4096, you could always divide that number by half down to unity, so that there would never be fractions. 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096.