tions of heterogeneous Rays,
and their various Mixtures and Proportions in every Mixture. By this
way of arguing I invented almost all the Phaenomena described in these
Books, beside some others less necessary to the Argument; and by the
successes I met with in the Trials, I dare promise, that to him who
shall argue truly, and then try all things with good Glasses and
sufficient Circumspection, the expected Event will not be wanting. But
he is first to know what Colours will arise from any others mix'd in any
assigned Proportion.

_PROP._ IV. THEOR. III.

_Colours may be produced by Composition which shall be like to the
Colours of homogeneal Light as to the Appearance of Colour, but not as
to the Immutability of Colour and Constitution of Light. And those
Colours by how much they are more compounded by so much are they less
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
AEquilibrion, 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 whit