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the dark wall in which this window is, be b s, that is, one of the
sides of the wall.
Then we may say that the line p h is darker than any other part of
the space o p c h, because this line faces the whole surface in
shadow of [Footnote: In the original the diagram is placed between
lines 27 and 28.] the wall b s. The line o c is lighter than the
other part of this space o p c h, because this line faces the
luminous space a b.
Where the shadow is larger, or smaller, or equal the body which
casts it.
[First of the character of divided lights. [Footnote 14: lumi
divisi. The text here breaks off abruptly.]
OF THE COMPOUND SHADOW F, R, C, H CAUSED BY A SINGLE LIGHT.
The shadow f r c h is under such conditions as that where it is
farthest from its inner side it loses depth in proportion. To prove
this:
Let d a, be the light and f n the solid body, and let a e be
one of the side walls of the window that is d a. Then I
say--according to the 2nd [proposition]: that the surface of any
body is affected by the tone of the objects surrounding it,--that
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