Of the edges [outlines] of shadows. Some have misty and ill defined
edges, others distinct ones.

No opaque body can be devoid of light and shade, except it is in a
mist, on ground covered with snow, or when snow is falling on the
open country which has no light on it and is surrounded with
darkness.

And this occurs [only] in spherical bodies, because in other bodies
which have limbs and parts, those sides of limbs which face each
other reflect on each other the accidental [hue and tone] of their
surface.

An experiment.