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by its colour, as well as by form and size. But if the intercepting
plane has in it some small perforation opening into a darker
chamber--not darker in colour, but by absence of light--you will see
the rays enter through this hole and transmitting to the plane
beyond all the details of the object they proceed from both as to
colour and form; only every thing will be upside down. But the size
[of the image] where the lines are reconstructed will be in
proportion to the relative distance of the aperture from the plane
on which the lines fall [on one hand] and from their origin [on the
other]. There they intersect and form 2 pyramids with their point
meeting [a common apex] and their bases opposite. Let a b be the
point of origin of the lines, d e the first plane, and c the
aperture with the intersection of the lines; f g is the inner
plane. You will find that a falls upon the inner plane below at
g, and b which is below will go up to the spot f; it will be
quite evident to experimenters that every luminous body has in
itself a core or centre, from which and to which all the lines
radiate which are sent forth by the surface of the luminous body and
reflected back to it; or which, having been thrown out and not
intercepted, are dispersed in the air.
1
31.
THE RAYS WHETHER SHADED OR LUMINOUS HAVE GREATER STRENGTH
AND EFFECT
AT THEIR POINTS THAN AT THEIR SIDES.
116
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