wish to repeat them.

1. _Of direct and inverse spectra existing at the same time_; _of
reciprocal direct spectra_; _of a combination of direct and inverse
spectra_; _of a spectral halo_; _rules to pre-determine the colours of
spectra_.

a. When an area, about six inches square, of bright pink Indian paper, had
been viewed on an area, about a foot square, of white writing paper, the
internal spectrum in the closed eye was green, being the reverse spectrum
of the pink paper; and the external spectrum was pink, being the direct
spectrum of the pink paper. The same circumstance happened when the
internal area was white, and external one pink; that is, the internal
spectrum was pink, and the external one green. All the same appearances
occurred when the pink paper was laid on a black hat.

b. When six inches square of deep violet polished paper was viewed on a
foot square of white writing paper, the internal spectrum was yellow, being
the reverse spectrum of the violet paper, and the external one was violet,
being the direct spectrum of the violet paper.

c. When six inches square of pink paper was viewed on a foot square of blue
paper, the internal spectrum was blue, and the external spectrum was pink;
that is, the internal one was the direct spectrum of the external object,
and the external one was the direct spectrum of the internal object,
instead of their being each the reverse spectrum of the objects they
belonged to.

d. When six inches square of blue paper were viewed on a foot square of
yellow paper, the interior spectrum became a brilliant yellow, and the
exterior one a brilliant blue. The vivacity of the spectra was owing to
their being excited both by the stimulus of the interior and exterior
objects; so that the interior yellow spectrum was both the reverse spectrum
of the blue paper, and the direct one of the yellow paper; and the exterior
blue spectrum was both the reverse spectrum of the yellow paper, and the
direct one of the blue paper.

e. When the internal area was only a square half-inch of red paper, laid on
a square foot of dark violet paper, the internal spectrum was green, with a
reddish-blue halo. When the red internal paper was two inches square, the
internal spectrum was a deeper green, and the external one redder. When the
internal paper was six inches square, the spectrum of it became blue, and
the spectrum of the external paper was red.

f. When a square half-inch of blue paper was lai