full and intense, and by too much Composition they maybe diluted and
weaken'd till they cease, and the Mixture becomes white or grey. There
may be also Colours produced by Composition, which are not fully like
any of the Colours of homogeneal Light._
For a Mixture of homogeneal red and yellow compounds an Orange, like in
appearance of Colour to that orange which in the series of unmixed
prismatick Colours lies between them; but the Light of one orange is
homogeneal as to Refrangibility, and that of the other is heterogeneal,
and the Colour of the one, if viewed through a Prism, remains unchanged,
that of the other is changed and resolved into its component Colours red
and yellow. And after the same manner other neighbouring homogeneal
Colours may compound new Colours, like the intermediate homogeneal ones,
as yellow and green, the Colour between them both, and afterwards, if
blue be added, there will be made a green the middle Colour of the three
which enter the Composition. For the yellow and blue on either hand, if
they are equal in quantity they draw the intermediate green equally
towards themselves in Composition, and so keep it as it were in
quilibrion, that it verge not more to the yellow on the one hand, and
to the blue on the other, but by their mix'd Actions remain still a
middle Colour. To this mix'd green there may be farther added some red
and violet, and yet the green will not presently cease, but only grow
less full and vivid, and by increasing the red and violet, it will grow
more and more dilute, until by the prevalence of the added Colours it be
overcome and turned into whiteness, or some other Colour. So if to the
Colour of any homogeneal Light, the Sun's white Light composed of all
sorts of Rays be added, that Colour will not vanish or change its
Species, but be diluted, and by adding more and more white it will be
diluted more and more perpetually. Lastly, If red and violet be mingled,
there will be generated according to their various Proportions various
Purples, such as are not like in appearance to the Colour of any
homogeneal Light, and of these Purples mix'd with yellow and blue may be
made other new Colours.
_PROP._ V. THEOR. IV.
_Whiteness and all grey Colours between white and black, may be
compounded of Colours, and the whiteness of the Sun's Light is
compounded of all the primary Colours mix'd in a due Proportion._
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