THE DISCRIMINATION OF COLOUR

Abstract

In a paper on the relation of light perception to colour perception, and in previous writings, I have stated that if a portion of the spectrum be isolated, it will appear monochromatic, the length of the monochromatic region varying with the intensity and wave-length of the light and the colour perception of the observer. Most normal sighted persons make about eighteen such divisions in a bright spectrum. In a paper in the ‘Proceedings of the Royal Society,' Lord Rayleigh, whilst agreeing that the facts were as I stated in the conditions described by me, expressed the opinion that he could distinguish between the wavelengths included in a monochromatic division to the extent of discriminating between the colours of the two D lines. Lord Rayleigh kindly lent me the colour box with which he had made the experiments, and, on repeating them in the manner described by him, I arrived at similar results. I hope, however, to be able to show that the results obtained by Lord Rayleigh were due to the admixture of small quantities of white and coloured light and to certain physiological influences which had not been taken into consideration, and which prevented him from arriving at a correct interpretation of the colours.