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To the Editor.
—There is an important error in the article "Colorimetry by a New Principle" by Gunkel and Cogan (Archives 96:331-334, 1978) that should not pass uncorrected. Under the heading "A practical chromaticity system," the authors attribute the discovery of the chromaticity circle to Sir Isaac Newton. Newton most certainly did speculate that the locus of spectrum colors and the most saturated nonspectral purples could be represented by a circle, and proposed a "center-of-gravity" principle in predicting the color appearance of various mixtures of primary colors. This is quite different from the development of chromaticity diagrams that came much later. What is common to both, however, is Newton's concept that primary colors could be treated as masses, or, in more modern parlance, vectors that add linearly. These properties are embodied in the trichromatic principle of color mixture, and the positions (or chromaticities) of mixtures of any set of primary
Moreland JD. The Chromaticity Circle. Arch Ophthalmol. 1979;97(12):2398. doi:10.1001/archopht.1979.01020020603023