Colour in Nature e-bog

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. The literature of the subject is so extensive that it has been found impossible within the assigned limits of space to attempt a complete bibliography. I have therefore thought it most advisable to confine myself as far as possible in the list of references to papers actually consulted and discussed in the text. Even thus abbreviated, the list will, I trust, be of value to the workers in the subject.