“As with sounds, so with colours. At each end of the solar spectrum the chemist can detect the presence of what are known as ‘actinic’ rays. They represent colours—integral colours in the composition of light—which we are unable to discern. The human eye is an imperfect instrument; its range is but a few octaves of the real ‘chromatic scale.’ I am not mad; there are colours that we cannot see.

“And, God help me! the Damned Thing is of such a colour!”