A Sphere Lit by a Broad Source, Casting a Shadow Pyramid
Rays from an arc-shaped luminous body converge on a sphere and throw graded shade
A wide arc, standing for an extended luminous source, spans the upper half of the sheet and is flanked by short captioned rectangles. From it numerous rays descend and cross to strike a banded sphere set low on the page, which throws a triangular pyramid of shade below rendered in flat and hatched tone. The figure studies how a broad light bounds the core shadow and the softer penumbra of a round body. The surrounding mirror-written Italian is not transcribed in this bundle, and further untranscribed text is present.
On this page
Broad source, sphere, and derived shadow
An arc at the top represents an extended light, with two small labelled panels at its ends. Rays run down and cross to fall on a banded sphere below, which casts a triangular shaded region divided into a darker core and lighter margins. The construction distinguishes total shadow from graded penumbra produced by a wide source.
Accompanying argument (untranscribed)
Several lines of mirror-written Italian head the sheet and continue in a block below the figure, keyed to the lettered points of the diagram. This text is not supplied in the bundle and is not transcribed here.