white. So also if the red and violet be
intercepted, the remaining yellow, green and blue, will compound a green
upon the Paper, and then the red and violet being let pass will fall
upon this green, and together with it decompound a white. And that in
this Composition of white the several Rays do not suffer any Change in
their colorific Qualities by acting upon one another, but are only
mixed, and by a mixture of their Colours produce white, may farther
appear by these Arguments.

[Illustration: FIG. 6.]

If the Paper be placed beyond the Focus G, suppose at [Greek: de], and
then the red Colour at the Lens be alternately intercepted, and let pass
again, the violet Colour on the Paper will not suffer any Change
thereby, as it ought to do if the several sorts of Rays acted upon one
another in the Focus G, where they cross. Neither will the red upon the
Paper be changed by any alternate stopping, and letting pass the violet
which crosseth it.

And if the Paper be placed at the Focus G, and the white round Image at
G be viewed through the Prism HIK, and by the Refraction of that Prism
be translated to the place _rv_, and there appear tinged with various
Colours, namely, the violet at _v_ and red at _r_, and others between,
and then the red Colours at the Lens be often stopp'd and let pass by
turns, the red at _r_ will accordingly disappear, and return as often,
but the violet at _v_ will not thereby suffer any Change. And so by
stopping and letting pass alternately the blue at the Lens, the blue at
_v_ will accordingly disappear and return, without any Change made in
the red at _r_. The red therefore depends on one sort of Rays, and the
blue on another sort, which in the Focus G where they are commix'd, do
not act on one another. And there is the same Reason of the other
Colours.

I considered farther, that when the most refrangible Rays P_p_, and the
least refrangible ones T_t_, are by converging inclined to one another,
the Paper, if held very oblique to those Rays in the Focus G, might
reflect one sort of them more copiously than the other sort, and by that
Means the reflected Light would be tinged in that Focus with the Colour
of the predominant Rays, provided those Rays severally retained their
Colours, or colorific Qualities in the Composition of White made by them
in that Focus. But if they did not retain them in that White, but became
all of them severally endued there with a Disposition to strike the
Sense wit