The pouring vessel: motions resolved into a right triangle
Natural and transverse motion as the two legs, the falling stream as the hypotenuse
Both sides are given over to Leonardo's analysis of compound motion using a vessel that pours: the transverse motion of the vessel and the natural (downward) motion of the poured matter form the two legs of a right angle whose hypotenuse is the falling stream. He works out how doubling the weight or the speed changes the proportions of the triangle, and lays out a scale in which the degrees of motion along side a f are successively halved (e l, d K, c i, b h). On the recto he asks why a continuous falling quantity settles along the same oblique line as a discontinuous, broken stream, and closes with a device in which the weight n is raised without extra effort. A marginal note adds that each falling body is enclosed in glass so the buffeting of the air cannot impede it.
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Transverse and natural motion make a right angle
The transverse motion of the pouring vessel and the natural motion of the poured matter create the two sides of a right angle, whose hypotenuse is the thing that pours. When the transverse motion equals the natural motion, the hypotenuse cuts the two sides equally.
Doubling weight or speed changes the triangle
If the natural motion is doubled in weight it is doubled in speed, so the hypotenuse no longer cuts the sides equally: the natural side becomes double the transverse. Likewise if the transverse speed is doubled, the hypotenuse cuts the sides in double proportion.
Degrees of motion halved along side a f
The degrees of motion are measured on side a f, which is always divided in half at each cut, so that the degrees and minutes are of equal spaces: the two parts of e l match each of the four of d K, the eight of c i match those four, the sixteen of b h match the eight, and the thirty-two each match the sixteen.
The poured stream as an oblique hypotenuse (b, n)
The discontinuous hypotenuse b n has its lower part farther from the transverse motion, because the extremity b was the first to separate from a; the part that separated last stays higher, nearer the mouth of the vessel from which the bodies descend.
Why a continuous falling quantity follows the oblique line
Leonardo asks why a continuous quantity, lacking the piecewise descent of a broken stream, still settles along its hypotenuse just as the discontinuous does. He reasons that, the weight being uniformly distributed along its cord, every particle falls perpendicularly beneath the line of the transverse motion, so the stream comes to rest obliquely as the hypotenuse of the right angle.
The weight n raised without extra effort
In a group of three lettered figures at the lower right, Leonardo notes that the weight n is raised without any increase of effort to its mover.
