Why a plunging river runs faster on top; a glass tank test
A cascade and a glass-plate vessel for watching which water reaches an outlet
The upper note argues that rivers of equal bed and width which plunge at their end run faster above than below, because the upper water falls more swiftly and the water behind must take up the same motion. Below, a drawing of a cascade is labelled simply 'Experiment', and a second drawing shows a rectangular vessel built of flat glass plates with a wooden back. The final note explains how to use such a glass tank, clouding the water with badly-mashed paper, to see which water (from the top, middle, or elsewhere) reaches an outlet opened at the bottom of a cistern.
On this page
Upper water runs faster where a river plunges
By the reasoning already given, rivers of equal bed and width that plunge down at their end run faster above than below, because at the fall the upper water is swifter than the lower. The water that successively leans upon it must take on that same motion.
A glass tank to see which water reaches the outlet
To learn which water reaches an outlet opened at the bottom of a cistern — whether from the top, the middle, or elsewhere — Leonardo directs making the vessel of flat glass plates, as shown, clouding the water with badly-mashed paper and noting the motion of the particles as it pours out. A cascade drawn alongside is marked 'Experiment', and the glass vessel is noted as having a wooden back.