Note 125 — Chapter VIII

“It may also be observed that the rays effective in destroying a given tint are, in a great many cases, those whose union produces a colour complementary to the tint destroyed, or at least one belonging to that class of colours to which such complementary tint may be referred. For example, yellows tending towards orange are destroyed with more energy by the blue rays; blue by the red, orange, and yellow rays; purples and pinks by yellow and green rays.”—Sir J. F. W. Herschel, On the action of the rays of the Solar Spectrum on Vegetable Colours: Phil. Trans., vol. cxxxiii. 1842.