The Artificial Spectrum Top

I HAVE read with interest Prof. Living's theory of my artificial spectrum top as summarised in NATURE of Dec. 13, p. 167, and am sorry I did not know of his conclusions before he made them public, because a very simple experiment would, I think, have convinced him of their inaccuracy. If Prof. Liveing, or any of your readers, will examine my top rotated in the light of a bright sodium flame, they will find that the colours are quite distinct. I know of no other way of seeing blue and red by the, light of sodium, and the phenomenon, I think, shows-decisively that the colours of the top are “artificial” sensations in the sense explained in my theory of the instrument.