Falling water currents: collisions, planking scour, and rebound
Intersecting jets, unequal falls that merge, scouring below planks, and water dividing on impact
This page gathers observations on water falling and colliding in the air, illustrated by three sketches at the right. Leonardo notes that intersecting falls of water fill with air in their rebound, and that when two equal falls strike, the one descending from the higher point of its reservoir merges into and ends within the course of the lower. He describes how water running off the end of planking scours the bed deeply, the fall growing more powerful at greater depths, and concludes that any water striking the bottom or an obstacle divides and runs off in different directions, the more so the stiller the pool.
On this page
Intersecting water falls fill with air in their rebound
The falls of water that cross one another in the air fill with air during their reflected motion. The rebound draws air into the crossing streams.
Two equal falls: the higher merges into the lower
Of two water falls of equal thickness that strike each other in the air, the one descending from the higher point of its reservoir joins the course of the lower one. With the lower fall it then ends its course.
Scouring where water runs off the end of planking
Water that runs over planking and then falls off its far edge breaks the bed greatly at the end of the planks. It lifts the bottom and deepens it the longer it falls, since the fall grows more powerful in greater depths than in lesser.
Water dividing when it strikes the bottom
Any water that strikes the bottom or another obstacle divides and runs off in different directions. Water that surges likewise divides at the surface and runs off in different directions, the more so the stiller the pool.