cal
Colours are Light it self Modify'd by Refractions chiefly, with a
concurrence sometimes of Reflections, and perhaps some other Accidents
depending on these two; if these Emphatical Colours be resolv'd to be
Genuine, it will seem consequent, that Colours, or at least divers of them,
are but Diversify'd Light, and not such Real and Inherent qualities as they
are commonly thought to be.

2. Now since we are wont to esteem the Echoes and other Sounds of Bodies,
to be True Sounds, all their Odours to be True Odours, and (to be short)
since we judge other Sensible Qualities to be True ones, because they are
the proper Objects of some or other of our Senses, I see not why Emphatical
Colours, being the proper and peculiar Objects of the Organ of Sight, and
capable to Affect it as Truly and as Powerfully as other Colours, should be
reputed but Imaginary ones.

And if we have (which perchance you'l allow) formerly evinc'd Colour, (when
the word is taken in its more Proper sense) to be but Modify'd Light, there
will be small Reason to deny these to be true Colours, which more
manifestly than others disclose themselves to be produc'd by
Diversifications of the Light.

3. There is indeed taken notice of a Difference betwixt these Apparent
colours, and those that are wont to be esteem'd Genuine, as to the
Duration, which has induc'd some Learned Men to call the former rather
Evanid than Fantastical. But as the Ingenious _Gassendus_ does somewhere
Judiciously observe, if this way of Arguing were Good, the Greeness of a
Leaf ought to pass for Apparent, because, soon Fading into a Yellow, it
Scarce lasts at all, in comparison of the Greeness of an Emerauld. I shall
add, that if the Sun-beams be in a convenient manner trajected through a
Glass-prism, and thrown upon some well-shaded Object within a Room, the
Rain-bow thereby Painted on the Surface of the Body that Terminates the
Beams, may oftentimes last longer than Some Colours I have produc'd in
certain Bodies, which would justly, and without scruple be accounted
Genuine Colours, and yet suddenly Degenerate, and lose their Nature.

4. A greater Disparity betwixt Emphatical Colours, and others, may perhaps
be taken from this, that Genuine Colours seem to be produc'd in Opacous
Bodies by Reflection, but Apparent ones in Diaphanous Bodies, and
principally by Refraction, I say Principally rather than Solely, because in
some cases Reflection also may concurr, but still this seems no