Part of the Colours by the interposed Tooth, whilst the rest of them
went on through the Interval of the Teeth to the Paper DE, and there
painted a round Solar Image. But the Paper I had first placed so, that
the Image might appear white as often as the Comb was taken away; and
then the Comb being as was said interposed, that Whiteness by reason of
the intercepted Part of the Colours at the Lens did always change into
the Colour compounded of those Colours which were not intercepted, and
that Colour was by the Motion of the Comb perpetually varied so, that in
the passing of every Tooth over the Lens all these Colours, red, yellow,
green, blue, and purple, did always succeed one another. I caused
therefore all the Teeth to pass successively over the Lens, and when the
Motion was slow, there appeared a perpetual Succession of the Colours
upon the Paper: But if I so much accelerated the Motion, that the
Colours by reason of their quick Succession could not be distinguished
from one another, the Appearance of the single Colours ceased. There was
no red, no yellow, no green, no blue, nor purple to be seen any longer,
but from a Confusion of them all there arose one uniform white Colour.
Of the Light which now by the Mixture of all the Colours appeared white,
there was no Part really white. One Part was red, another yellow, a
third green, a fourth blue, a fifth purple, and every Part retains its
proper Colour till it strike the Sensorium. If the Impressions follow
one another slowly, so that they may be severally perceived, there is
made a distinct Sensation of all the Colours one after another in a
continual Succession. But if the Impressions follow one another so
quickly, that they cannot be severally perceived, there ariseth out of
them all one common Sensation, which is neither of this Colour alone nor
of that alone, but hath it self indifferently to 'em all, and this is a
Sensation of Whiteness. By the Quickness of the Successions, the
Impressions of the several Colours are confounded in the Sensorium, and
out of that Confusion ariseth a mix'd Sensation. If a burning Coal be
nimbly moved round in a Circle with Gyrations continually repeated, the
whole Circle will appear like Fire; the reason of which is, that the
Sensation of the Coal in the several Places of that Circle remains
impress'd on the Sensorium, until the Coal return again to the same
Place. And so in a quick Consecution of the Colours the Impression of
every Colour remains in the Sensorium, until a Revolution of all the
Colours be compleated, and that first Colour return again. The
Impressions therefore of all the successive Colours are at once in the
Sensorium, and jointly stir up a Sensation of them all; and so it is
manifest by this Experiment, that the commix'd Impressions of all the
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