_PROP._ I. THEOR. I.
_The Ph nomena of Colours in refracted or reflected Light are not caused
by new Modifications of the Light variously impress'd, according to the
various Terminations of the Light and Shadow_.
The PROOF by Experiments.
_Exper._ 1. For if the Sun shine into a very dark Chamber through an
oblong hole F, [in _Fig._ 1.] whose breadth is the sixth or eighth part
of an Inch, or something less; and his beam FH do afterwards pass first
through a very large Prism ABC, distant about 20 Feet from the hole, and
parallel to it, and then (with its white part) through an oblong hole H,
whose breadth is about the fortieth or sixtieth part of an Inch, and
which is made in a black opake Body GI, and placed at the distance of
two or three Feet from the Prism, in a parallel Situation both to the
Prism and to the former hole, and if this white Light thus transmitted
through the hole H, fall afterwards upon a white Paper _pt_, placed
after that hole H, at the distance of three or four Feet from it, and
there paint the usual Colours of the Prism, suppose red at _t_, yellow
at _s_, green at _r_, blue at _q_, and violet at _p_; you may with an
Iron Wire, or any such like slender opake Body, whose breadth is about
the tenth part of an Inch, by intercepting the Rays at _k_, _l_, _m_,
_n_ or _o_, take away any one of the Colours at _t_, _s_, _r_, _q_ or
_p_, whilst the other Colours remain upon the Paper as before; or with
an Obstacle something bigger you may take away any two, or three, or
four Colours together, the rest remaining: So that any one of the
Colours as well as violet may become outmost in the Confine of the
Shadow towards _p_, and any one of them as well as red may become
outmost in the Confine of the Shadow towards _t_, and any one of them
may also border upon the Shadow made within the Colours by the Obstacle
R intercepting some intermediate part of the Light; and, lastly, any one
of them by being left alone, may border upon the Shadow on either hand.
All the Colours have themselves indifferently to any Confines of Shadow,
and therefore the differences of these Colours from one another, do not
arise from the different Confines of Shadow, whereby Light is variously
modified, as has hitherto been the Opinion of Philosophers. In trying
these things 'tis to be observed, that by how much the holes F and H are
narrower, and the Intervals between them and the Prism greater, and the
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