Yellow, may be made more faint: And even _Vermilion_ it self may, by too
much grinding, be brought to the colour of _Red-lead_, which is but an
Orange colour, which is confest by all to be very much upon the Yellow.
Now, though perhaps somewhat of this _diluting_ of _Vermilion_ by overmuch
grinding may be attributed to the Grindstone, or muller, for that some of
their parts may be worn off and mixt with the colour, yet there seems not
very much, for I have done it on a Serpentine-stone with a muller made of a
Pebble, and yet observ'd the same effect follow.

And secondly, as to the other of these operations on colours, that is, the
deepning of them, Limners and Painters colours are for the most part also
uncapable. For they being for the most part _opacous_; and that
_opacousness_, as I said before, proceeding from the particles, being very
much flaw'd, unless we were able to joyn and re-unite those flaw'd
particles again into one piece, we shall not be able to deepen the colour,
which since we are unable to do with most of the colours which are by
Painters accounted _opacous_, we are therefore unable to deepen them by
adding more of the same kind.

But because all those _opacous_ colours have two kinds of beams or Rays
reflected from them, that is, Rays unting'd, which are onely reflected from
the outward surface, without at all penetrating of the body, and ting'd
Rays which are reflected from the inward surfaces or flaws after they have
suffer'd a two-fold refraction; and because that transparent liquors mixt
with such _corpuscles_, do, for the most part, take off the former kind of
reflection; therefore these colours mixt with Water or Oyl, appear much
deeper than when dry, for most part of that white reflection from the
outward surface is remov'd. Nay, some of these colours are very much
deepned by the mixture with some transparent liquor, and that because they
may perhaps get between those two flaws, and so consequently joyn two or