And ev'n with Diaphanous Bodies, that are
Colour'd, there may be this way a Greater Degree of Whiteness produced,
than one would lightly think; as I remember, I have by Contusion obtain'd
Whitish Powders of _Granates_, Glass of _Antimony_, and _Emeralds_ finely
Beaten, and you may more easily make the Experiment, by taking Good
Venereal _Vitriol_ of a Deep Blew, and comparing with some of the Entire
Crystalls purposely reserv'd, some of the Subtile Powder of the same Salt,
which will Comparatively exhibit a very considerable degree of Whitishness.
13. Seventhly, And as by a 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.
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