Which wall is more lit past an opaque body
Light and shadow: the part seen by a greater sum of the pupil appears the more illuminated.
A note on light and shade: among walls of equal distance and quality, seen beyond the edges of an opaque body placed in front, that part appears the more illuminated which is seen by a greater portion of the pupil. Two red-chalk diagrams accompany the text, one at the top showing a shaded cone of light meeting a round opaque body, and one at the bottom with crossing rays between two circles. The chalk is faint but the geometry of the light-cones is clear.
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Illumination of walls seen past an opaque body
Among walls of equal distance and quality, seen beyond the edges of an opaque body set in front, that part appears more illuminated which is seen by a greater sum of the pupil. Visibility of the illuminated surface is thus tied to how much of the pupil takes it in.
Diagrams of light-cones and an opaque sphere
Two diagrams show a cone of light meeting a round opaque body: at the top a shaded beam with the interposed circle casting a shadow, and at the bottom crossing rays drawn between two circles. They illustrate the geometry of the accompanying note.