Shadow gradation and gravel on the river bed
How primary and derived shadow darken; where gravel settles after the water's bounce
At the top, two red-chalk 'shadowed bodies' illustrate a rule of shading: the primary shadow grows less dark the farther it lies from its edges, while the derived shadow bordering the primary is darker than the primary itself. Below, two river-bed studies concern gravel: water falling nearer to the perpendicular drives out less coarse gravel, and the gravel always settles after the bounce of the water (labelled b a f c), being struck at f.
On this page
Gradation of primary and derived shadow
The part of the primary shadow farthest from its edges is the least dark. The derived shadow that borders on the primary shadow is darker than the primary shadow itself.
Gravel settling after the water's bounce (b a f c)
The gravel always settles after the bounce of the water a b, being struck at f. The bed is labelled with the points b a f c.
Perpendicular fall and coarse gravel
Water that falls nearer to its perpendicular drives out less coarse gravel from the river bed.