varying the thicknesses of the Wedges, and consequently the tincture of the
Rays that past through the two holes, and sometimes also by varying the
Paper, that is, insteed of a white Paper, holding a gray, or a black piece
of Paper.

Whence I experimentally found what I had before imagin'd, that all the
varieties of colours imaginable are produc'd from several degrees of these
two colours, namely, Yellow and Blue, or the mixture of them with light and
darkness, that is, white and black. And all those almost infinite varieties
which Limners and Painters are able to make by compounding those several
colours they lay on their Shels or _Palads_, are nothing else, but some
_compositum_, made up of some one or more, or all of these four.

Now, whereas it may here again be objected, that neither can the Reds be
made out of the Yellows, added together, or laid on in greater or less
quantity, nor can the Yellows be made out of the Reds though laid never so
thin; and as for the addition of White or Black, they do nothing but either
whiten or darken the colours to which they are added, and not at all make
them of any other kind of colour: as for instance, _Vermilion_, by being
temper'd with White Lead, does not at all grow more Yellow, but onely there
is made a whiter kind of Red. Nor does Yellow _Oker_, though laid never so
thick, produce the colour of _Vermilion_, nor though it be temper'd with
Black, does it at all make a Red; nay, though it be temper'd with White, it
will not afford a fainter kind of Yellow, such as _masticut_, but onely a
whiten'd Yellow; nor will the Blues be _diluted_ or deepned after the
manner I speak of, as _Indico_ will never afford so fine a Blue as
_Ultramarine_ or _Bise_; nor will it, temper'd with _Vermilion_, ever
afford a Green, though each of them be never so much temper'd with white.

To which I answer, that there is a great difference between _diluting_ a