A text-book of general astronomy : for colleges and scientific schools (1888)
Young, Charles A. (Charles Augustus), 1834-1908 · Boston ; London : Ginn & Company · leaf 210
to the presence inthe suns lower atmosphere ofknown terrestrial elements in thestate of vapor. To effect the coni- parison necessary for this purpose,the spectroscope must be so arranged that the observer can have beforehim, side by side, the spectrum of sunlight and that of the substanceto be… … Fig. 110. — The Comparison Prism. 198 THE SIN. the light of some flame or electric spark. On looking into the eye-piece of the spectroscope, the observer will then see a spectrum, thelower half of which, for instance, is made by sunlight, while theupper half is made by light coming from an electric…
Astronomy
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