At one hour of day the air toward the south, near the horizon, has a middling darkness of reddish clouds, and toward the west it grows dark, and toward the east the moisture of the horizon is clearer than the horizon of the air, and the white of the buildings to the east is little discernible; and at midday the farther they recede the more they become dark and reddish, and more so toward the west; and the shadows do the contrary, for they are consumed before the white. ... to the east, and the trees are seen more in their crowns than at their feet, because the air thickens more below and the building darkens more above. And the trees are little discernible, because of the dark vapour to the west and the clear vapour to the east, in the southern part.

Whatever moves by means of another makes a motion proportional to the motion of its mover; but it is an inverse proportion, because, this proportion being from the motion of the mover to the motion of the moved as from the power of the moved to that of its mover, it is inverse; since the moved has a power of one and the mover a power of a hundred, it follows that the moved will move a hundred when the mover moves one. How the strings of bows are made straight along their length, and how the strings of lutes should be made of silk or of gut. How the force of the bow is pyramidal, and likewise that of the bombard. Impetus is born equally from weight as from force.

a b; c n d. If these two bows are equal in shape and power, and the unbending of the one imparts of its force to the other, it will lend it neither more nor less than its half. But if the bows be in whatever proportion one wishes between themselves ...

Sometimes the impetuses are equal and sometimes one or the other is the greater. Every motion moved by another has two impetuses, that is, its own and that of its mover; when that of the mover fails, its own remains.

The thing that moves either moves downward or upward or crosswise or obliquely. And if it moves upward, at every degree of motion it loses velocity, and downward at every degree of motion it loses of the given impetus and acquires of its own natural motion. And if it be water, upward it thickens the more the more it moves, until the pyramid is formed where it acquires the first velocity. And if it moves downward ...

b - c a. b is faster than a and than c.

Because every course of a river is faster in the middle of its width than at the sides, and runs more at the surface than at the bottom, being of equal course, the mobile bridge made upon boats is of itself weaker in the middle of its length than toward the ends. Whence I conclude that, the greater weakness of the bridge being joined with the greater percussion of the water, this bridge will break in the middle.

Make it so that in the motion of the bridge the length of the boats is always found along the line of the current of the waters, and it will be so much the easier to move, the less percussion the boats have from the waters.