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Concerning the Gas-Flame, Electric, and Solar Spectra, and their Effects on the Eye


THE spectra of the light from these various sources is a subject to which I gave some attention about two years ago, and a detailed account of my experiments may be found in the Proceedings of the American Academy of Sciences for 1880, p. 236. In this article it was shown that the colour of the sun was not what the average person would call white, but decidedly bluish. The sun's “golden glare” spoken of by Mr. Capron is entirely a subjective effect (except when near the horizon); and follows from the well-known law that bright lights tend to look yellow, and faint ones blue. If the highly magnified images of two diaphragms equally illuminated, one by the electric light and one by the sun, be cast upon a screen, the distinctly bluish character of the latter will be strongly marked. Indeed, the magnesium light is more blue than the electric, and hence probably is of a higher temperature, although being spread through a larger space, has less available heating power. As far as mere colour is concerned then, the electric light approaches nearer to the sun than does the gas-flame.

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