Repeated Confluence and Divergence of River Currents
Where two currents collide they rise, scrape the bed, and scour depth
Leonardo studies what happens where two currents of water that begin apart converge and strike one another. After the collision they rise up; their bed is little consumed at first because they part from it, but as they fall back and break apart they strike and scrape the bottom, so that a scour of depth forms—something seen in the great currents of rivers. A second note, keyed to points S and a, explains that the little-worn rise of the bed keeps building up the point of collision, so that the falling water delivers an ever greater blow. Drawings show an hourglass-like convergence and divergence of streams and an S-shaped rebounding flow with a vortex.
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Colliding currents scour depth in the riverbed
Two currents beginning distant from one another converge on the place where they strike together; after the collision they rise, part from the bed, then fall back as they break apart and scrape the bottom with their motion. That beating and scraping is what produces depth there, as happens in the great currents of rivers.
Point a: the rising bed increases the force of the collision (S–a)
At the point marked a, the aforesaid collision occurs. The elevation of the bed, which is little consumed, always adds to raising the place of collision or junction, so that the water, falling from higher, delivers a greater blow.