A waterfall striking, rebounding, and hollowing its bed
Turbulent cascade with points f, m, g, n
A vigorous pen sketch of a turbulent cascade fills the upper page, with curling vortices where the falling sheet strikes the water below and the Bibliotheque de l'Institut stamp at left. The text traces how the water's percussion drives toward m and strikes the bank there, rebounds from the bottom, and turns back toward the lower surface. Meeting the second fall at f, where the water is already raised high by the leap, it cannot climb but submerges, passes beneath the earlier leap, turns back at n, and there hollows out the bottom.
On this page
Percussion, rebound and reversal of the falling water (f, m, g, n)
The percussion of water directs itself toward m and strikes the bank m, then rebounds from the bottom and turns back toward the lower surface. Finding the second fall at f, where the leap has already raised the water high, it cannot climb but submerges with that high water, which then descends. It is forced to pass beneath the earlier leap and turns back at n.
The current hollows out its bed at n
Where the reversed current turns back at n it hollows out the bottom, scouring the bed before passing on. The observation ties the water's rebounding motion to erosion of the channel floor.
Turbulent cascade drawn with curling vortices
The upper half of the sheet is a lively pen study of falling turbulent water, its surface broken into curling eddies and rolling vortices where the cascade meets the pool. The drawing visualises the very percussion and rebound the text analyses.