That which casts the shadow does not face it, because the shadows
are produced by the light which causes and surrounds the shadows.
The shadow caused by the light _e_, which is yellow, has a blue
tinge, because the shadow of the body _a_ is cast upon the pavement
at _b_, where the blue light falls; and the shadow produced by the
light _d_, which is blue, will be yellow at _c_, because the yellow
light falls there and the surrounding background to these shadows _b
c_ will, besides its natural colour, assume a hue compounded of
yellow and blue, because it is lighted by the yellow light and by
the blue light both at once.

Shadows of various colours, as affected by the lights falling on
them. That light which causes the shadow does not face it.

[Footnote: In the original diagram we find in the circle _e_
"_giallo_" (yellow) and the cirle _d_ "_azurro"_ (blue) and also
under the circle of shadow to the left "_giallo_" is written and
under that to the right "_azurro_".

In the second diagram where four circles are placed in a row we find
written, beginning at the left hand, "_giallo_" (yellow), "_azurro_"
(blue), "_verde_" (green), "_rosso_" (red).]

The effect of colours in the camera obscura (273-274).