Change of Position in the Parts, a Body that is
not White, may be made White, so by a Slight change of the Texture of its
Surface, a White Body may be Depriv'd of its Whiteness. For if, (as I have
try'd in Gold-smiths Shops) you take a piece of Silver that has been
freshly Boyl'd, as the Artificers call it, (which is done by, first
Brushing, and then Decocting it with Salt and Tartar, and perhaps some
other Ingredients) you shall find it to be of a Lovely White. But if you
take a piece of Smooth Steel, and therewith Burnish a part of it, which may
be presently done, you shall find that Part will Lose its Whiteness, and
turn a _Speculum_, looking almost every where Dark, as other
Looking-glasses do, which may not a little confirm our Doctrine. For by
this we may guess, what it is chiefly that made the Body White before, by
considering that all that was done to deprive it of that Whiteness, was
only to Depress the Little Protuberances that were before on the Surface of
the Silver into one Continu'd Superficies, and thereby effect this, that
now the Image of the Lucid Body, and consequently a Kind of Whiteness shall
appear to your Eye, but in some place of the greater Silver Looking-glass
(whence the Beams reflected at an Angle Equal to that wherewith they fall
on it, may reach your Eye) whilst the Asperity remain'd Undestroy'd, the
Light falling on innumerable Little _Specula_ Obverted some one way, and
some another, did from all Sensibly Distinguishable parts of the
Superficies reflect confus'd Beams or Representations of Light to the
Beholders Eye, from whence soever he chance to Look upon it. And among the
Experiments annex'd to this Discourse, you will find One, wherein by the
Change of Texture in Bodies, Whiteness is in a Trice both Generated and
Destroy'd.

* * * * *

CHAP. II.

1. What we have Discours'd of Whiteness, may somewhat Assist us to form a
Notion of Blackness, those two Qualities being Contrary enough to
Illustrate each other. Yet among the Antient _Philosophers_ I find less
Assistance to form a Notion of Blackness than of Whiteness, only
_Democritus_ in the passage above Recited out of _Aristotle_ has given a
General Hint of the Cause of this Colour, by referring the Blackness of
Bodies to their Asperity. But this I call but a General Hint, because those
Bodies that are Green, and Purple, and Blew, seem to be so as well as Black
ones, upon the Account of their Superficia