The Rays Whether Shaded or Luminous Have Greater Strength and Effect at Their Points than at Their Sides.
Although the points of luminous pyramids may extend into shaded places and those of pyramids of shadow into illuminated places, and though among the luminous pyramids one may start from a broader base than another; nevertheless, if by reason of their various length these luminous pyramids acquire angles of equal size their light will be equal; and the case will be the same with the pyramids of shadow; as may be seen in the intersected pyramids a b c and d e f, which though their bases differ in size are equal as to breadth and light.
[Footnote: 51—55: This supplementary paragraph is indicated as being a continuation of line 45, by two small crosses.]
The difference between light and lustre (132—135).
132.
Of the difference between light and lustre; and that lustre is not included among colours, but is saturation of whiteness, and derived from the surface of wet bodies; light partakes of the colour of the object which reflects it (to the eye) as gold or silver or the like.
133.