The falling water-vein and the descent of dropped bodies
Shape and continuity of a pouring jet, compared with accelerating falling balls
A densely written sheet investigating how water falls from a pipe: issuing from a full bore it drops uniform in thickness and swift, and Leonardo refutes the idea that a falling vein tapers to a pyramid, since that would make it weightless and motionless. Continuity is argued from a poured jug that fills an equal jug at every point of its descent, so equal quantity passes everywhere in equal time. He runs this alongside the descent of dropped balls, weighing whether their increments follow arithmetic or geometric progression, illustrated by a doubling column (1, 2, 4, 8 ... 65536) and an experiment releasing 25 blowpipe balls from a height. A closing passage advises mill-builders to feed the wheel through a long, even channel with a square water jet.
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Water from a full pipe falls uniform and swift
If water issues from a full pipe and pours out, it falls equal in thickness and without any intersection, and is swift in its motion. A vertical tube at the top of the sheet shows the case.
Why a falling vein cannot taper to a pyramid
Whoever believes water falls as a pyramid makes two errors: that the pyramid comes to nothing, and that it would become so light it would have no motion. Companion figures compare veins of continuous thickness with impossible tapering and widening ones.
Dropped balls: arithmetic versus geometric descent
A doubt arises over the descent of balls let fall at equal degrees of time. If the increments follow continuous arithmetic proportion, the second ball exceeds the first by double space but the hundredth by only a hundredth of an interval; if geometric, over a descent of a million miles the time of the last would not answer the time of the first at equal intervals.
Experiment: releasing 25 balls from a height
Drive 25 equal blowpipe balls into a barrel so they stand one perpendicularly above another, set them high, release with a string and stand below; though the motion will not let you read off the equal spaces. If a b makes one degree of descent in one degree of time, b c being swifter makes somewhat more, and so on.
Doubling series and a conversion of measures
A column doubles from 1 through 2, 4, 8, 16 up to 65536, the geometric progression underlying the descent argument, and a note fixes that a million braccia equals 333 miglia.
Advice to mill-builders on channel and water jet
Water is of swifter descent poured from a more even and long channel, slower from an uneven, short one. Those who make mills should first send the water through a long even channel; the jet striking the wheels should be square, as high as it is wide, and strike far from the wheel's center for greatest effect.
