Body Edges, a Figure in the Wind, and the Studio Window
Three rules of the Treatise on Painting, with an arch diagram and a striding figure
This page continues the Treatise on Painting with three chapters, two of them illustrated. The first explains how the edge of a convex body reads darker against a ground of the same colour, and how a straight rod appears dark on a white ground but bright on a dark one; a small arch-like diagram accompanies it. A second chapter states that a figure moving against the wind cannot keep its centre of gravity properly over its support, shown by a pen sketch of a striding figure at the lower centre, while a third prescribes the painter's studio window of oiled cloth, shaded gradually toward its edges.
On this page
Edges of convex bodies and rods against grounds of equal colour
When convex bodies terminate against other bodies of equal colour, the edge of the convex appears darker where it meets them. A level rod appears very dark on a white ground but, on a dark ground, brighter than any other part of it, even though the light falling on the rod is everywhere of equal brightness.
Diagram of an arched form illustrating light and dark edges
Between the two columns of text a small pen diagram of a semicircular arch is drawn, with ruled horizontal lines and faint rays converging below, illustrating how the edge of a convex or level form reads against its ground.
A figure striding forward against the wind
The figure that moves against the wind, by whatever path, cannot keep the centre of its gravity in due order over the centre of its support. The rule is illustrated by a pen sketch of a man striding and leaning forward at the lower centre of the page.
The painter's studio window, shaded toward its edges
Let the window of painters' rooms be made of oiled-cloth panes without cross-bars, darkened degree by degree toward its edges, so that the boundary of the lights is not joined with the boundary of the window.