riously colour'd at
the Lens, so the Colours which afterwards emerge out of it by new
Refractions are no other than those of which its Whiteness was
compounded. The Refraction of the Prism HIK _kh_ generates the Colours
PQRST upon the Paper, not by changing the colorific Qualities of the
Rays, but by separating the Rays which had the very same colorific
Qualities before they enter'd the Composition of the refracted beam of
white Light XY. For otherwise the Rays which were of one Colour at the
Lens might be of another upon the Paper, contrary to what we find.

So again, to examine the reason of the Colours of natural Bodies, I
placed such Bodies in the Beam of Light XY, and found that they all
appeared there of those their own Colours which they have in Day-light,
and that those Colours depend upon the Rays which had the same Colours
at the Lens before they enter'd the Composition of that beam. Thus, for
instance, Cinnaber illuminated by this beam appears of the same red
Colour as in Day-light; and if at the Lens you intercept the
green-making and blue-making Rays, its redness will become more full and
lively: But if you there intercept the red-making Rays, it will not any
longer appear red, but become yellow or green, or of some other Colour,
according to the sorts of Rays which you do not intercept. So Gold in
this Light XY appears of the same yellow Colour as in Day-light, but by
intercepting at the Lens a due Quantity of the yellow-making Rays it
will appear white like Silver (as I have tried) which shews that its
yellowness arises from the Excess of the intercepted Rays tinging that
Whiteness with their Colour when they are let pass. So the Infusion of
_Lignum Nephriticum_ (as I have also tried) when held in this beam of
Light XY, looks blue by the reflected Part of the Light, and red by the
transmitted Part of it, as when 'tis view'd in Day-light; but if you
intercept the blue at the Lens the Infusion will lose its reflected blue
Colour, whilst its transmitted red remains perfect, and by the loss of
some blue-making Rays, wherewith it was allay'd, becomes more intense
and full. And, on the contrary, if the red and orange-making Rays be
intercepted at the Lens, the Infusion will lose its transmitted red,
whilst its blue will remain and become more full and perfect. Which
shews, that the Infusion does not tinge the Rays with blue and red, but
only transmits those most copiously which were red-making before, and
refle