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2
58.
Of several objects equal in size, brightness of background and
length that which has the flattest surface will look the largest. A
bar of iron equally thick throughout and of which half is red hot,
affords an example, for the red hot part looks thicker than the
rest.
2
59.
Of several bodies of equal size and length, and alike in form and in
depth of shade, that will appear smallest which is surrounded by the
most luminous background.
2
60.
DIFFERENT PORTIONS OF A WALL SURFACE WILL BE DARKER OR BRIGHTER
IN
PROPORTION AS THE LIGHT OR SHADOW FALLS ON THEM AT A LARGER
ANGLE.
The foregoing proposition can be clearly proved in this way. Let us
say that m q is the luminous body, then f g will be the opaque
body; and let a e be the above-mentioned plane on which the said
angles fall, showing [plainly] the nature and character of their
bases. Then: a will be more luminous than b; the base of the
angle a is larger than that of b and it therefore makes a
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