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Published online by Cambridge University Press: 15 September 2014
The following beliefs regarding vision meet with very general acceptance:—
First. Very intense light of any wave-length produces practically the sensation of whiteness.
Second. Very weak light of any wave-length produces practically the sensation of whiteness.
Third. A coloured area of normal brightness retains its colour, though with diminished purity, when gazed at steadily for a long time.
Fourth. Small, faintly luminous, objects are seen more easily by indirect vision than by direct vision.