In a paper on “The Scattering of Light in the Refractive Media of the Eye” published in the Philosophical Magazíne, for November 1919 (p. 568), I discussed the explanation of the luminous effects observed when a small brilliant source of light is viewed directly by the eye against a dark background, and especially of the marked difference between the cases in which the source emits white light and highly monochromatic light respectively. In both cases the source appears to be surrounded by a diffraction-halo: but the structure of the halo is markedly different in appearance.