Experiment on the Descent of Grain Through a Vessel's Hole
Which grains fall first over the outlet, with notes on currents and waves in water
On this narrow strip Leonardo designs an experiment to learn which grains fall first when millet drains through a hole in the bottom of a vase: a paper tube of black millet (S f) is set inside white millet (m n) so the two colours can be told apart during the descent. He reasons that flow is fastest for the column standing perpendicular over the hole and that water, staying level on top, keeps its perpendicular in proportion to its transverse. Two further notes treat water running within water, the circular waves raised in a still pool struck by an incoming current, and how water draining below is replaced from above, tested with small floating seeds. A faint sketch of a flowing current appears in the lower-middle of the strip.
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Why the descent of the grain varies from start to finish
The millet varies throughout its fall because at first only the column standing perpendicular over the hole pours out; once the weight of that perpendicular part is spent, the flow no longer follows. Leonardo adds that water, being level on top, always keeps its perpendicular in proportion to the transverse.
The paper-tube apparatus for coloured millet (m S n f)
A thin paper is pasted around a uniform rod to form a tube; the rod is withdrawn and the tube filled with black millet and stopped. The tube then stops the vase's hole while the vase is filled with white panic-grass, so that pulling out the tube leaves the black millet 'clothed' in white.
Black grain versus white grain over the outlet (m n / S f)
Unstopping the vase quickly, one notes whether black or white grain descends first, to learn whether the black standing perpendicular over the hole, or the more remote white, falls soonest. Leonardo suspects that near the end the black will sink low while the white keeps high banks, so the white's weight may take the descent first.
Waves of water running within water
Water running within water cannot enter without some descent, so its waves and leaps arise by depth as much as by breadth. Still pool-water struck opposite its exit by an overcoming current takes a circular wave that pushes farther.
Water draining below is restored from above
Unstopping the vase below makes a hollow form on the surface above; small floating seeds show whether the water moves toward that hollow. If it does, the water pouring out below is continually replenished from above and its surface sinks uniformly.