Unpublished diagram, 'Spectrum as washed out by different classes of persons' by Frederick William Edridge-Green A spectrum diagram in coloured ink, labelled diagram B. Ten horizontal bars labelled figures 1-10 show various spectrums, starting with a full colour spectrum from red to violet at figure 1, with the variety of colours decreasing until figure 10, which shows simply a grey bar. Subject: Ophthalmology / Optics 1890