d Painters are
incapable of, to wit, _Vermilion_ and _Red-lead_, and _Oker_, because the
ting'd parts are so exceeding small, that the most curious Grindstones we
have, are not able to separate them into parts actually divided so small as
the ting'd particles are; for looking on the most curiously ground
_Vermilion_, and _Oker_, and _Red-lead_, I could perceive that even those
small _corpuscles_ of the bodies they left were compounded of many pieces,
that is, they seem'd to be small pieces compounded of a multitude of lesser
ting'd parts: each piece seeming almost like a piece of Red Glass, or
ting'd Crystal all flaw'd; so that unless the Grindstone could actually
divide them into smaller pieces then those flaw'd particles were, which
compounded that ting'd mote I could see with my _Microscope_, it would be
impossible to _dilute_ the colour by grinding, which, because the finest we
have will not reach to do in _Vermilion_ or _Oker_, therefore they cannot
at all, or very hardly be _diluted_.

Other colours indeed, whose ting'd particles are such as may be made
smaller, by grinding their colour, may be _diluted_. Thus several of the
Blues may be _diluted_, as _Smalt_ and _Bise_; and _Masticut_, which is
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