ppears not that the
Nature of the Body is Alter'd, but only that the Disposition of its Parts
in reference to the Incident Light is Chang'd, why may not the Whiteness be
accounted Emphatical too, which I shall shew anon to be Producible, barely
by such another change in Black Horn? and yet this so easily acquir'd
Whiteness seems to be as truly its Colour as the Blackness was before, and
at least is more Permanent than the Greenness of Leaves, the Redness of
Roses, and, in short, than the Genuine Colours of the most part of Nature's
Productions. It may indeed be further Objected, that according as the Sun
or other Luminous Body changes place, these Emphatical Colours alter or
vanish. But not to repeat what I have just now said, I shall add, that if a
piece of Cloath in a Drapers Shop (in such the Light being seldome Primary)
be variously Folded, it will appear of differing Colours, as the Parts
happen to be more Illuminated or more Shaded, and if you stretch it Flat,
it will commonly exhibit some one Uniform Colour, and yet these are not
wont to be reputed Emphatical, so that the Difference seems to be chiefly
this, that in the Case of the Rain-bow, and the like, the Position of the
Luminary Varies the Colour, and in the Cloath I have been mentioning, the
Position of the Object does it. Nor am I forward to allow that in all Cases
the Apparition of Emphatical Colours requires a Determinate position of the
Eye, for if Men will have the Whiteness of Froth Emphatical, you know what
we have already Inferr'd from thence. Besides, the Sun-beams trajected
through a Triangular Glass, after the manner lately mention'd, will, upon
the Body that Terminates them, Paint a Rain-bow, that may be seen whether
the Eye be plac'd on the Right Hand of it or the Left, or Above or Beneath
it, or Before or Behind it; and though there may appear some Little
Variation in the Colours of the Rain-bow, beheld from Differing parts of
the Room, yet such a Diversity may be also observ'd by an Attentive Eye in
Real Colours, look'd upon under the like Circumstances, Nor will it follow,
that because there remains no Footsteps of the Colour upon the Object, when
the Prism is Remov'd, that therefore the Colour was not Real, since the
Light was truly Modify'd by the Refraction and Reflection it Suffer'd in
its Trajection through the Prism; and the Object in our case serv'd for a
Specular Body, to Reflect that Colour to the Eye. And that you may not be
Startled,