placed behind. And then by stopping any of the Colours _p_, _q_, _r_,
_s_, _t_, at the Lens, I found that the same Colour would vanish at the
Paper. So if the Purple _p_ was stopp'd at the Lens, the Purple P upon
the Paper would vanish, and the rest of the Colours would remain
unalter'd, unless perhaps the blue, so far as some purple latent in it