THE 
AMERICAN 
JOURNAL OF SCIENCE AND ARTS. 
[THIRD SERIES] 
Art. XIV.—Discovery of Oxygen in the Sun by Photography, and 
a new Theory of the Solar Spectrum ;* by Professor HENRY 
Draper, M.D. 
I PROPOSE in this preliminary paper to indicate the means 
by which I have discovered oxygen and probably nitrogen in 
the sun, and also to present a new view of the constitution o 
the solar spectrum. 
Oxygen discloses itself by bright lines or bands in the solar spec- 
trum, and does not give dark absorption lines like the metals. 
We must therefore change our theory of the solar spectrum 
and no longer regard it merely as a continuous spectrum with 
certain rays absorbed by a layer of ignited metallic vapors, but 
as having also bright lines and bands superposed on the back- 
ground of continuous spectrum. Such a conception not only 
opens the way to the discovery of others of the non-metals, 
sulphur, phosphorus, selenium, chlorine, bromine, iodine, 
fluorine, carbon, etc., but also may account for some of the 
so-called dark lines by regarding them as intervals between 
bright lines. 
It must be distinctly understood that in speaking of the 
solar spectrum here, I do not mean the spectrum of any limited 
area upon the dise or margin of the sun, but the spectrum of 
light from the whole disc. I have not used an image of the 
sun upon the slit of the spectrocope, but have employed the 
_ beam reflected from the flat mirror of the heliostat without any 
_ condenser. 
* Read before the American Philosophical Society, July 20th, 1877. 
Am. Jour. Sc1.—Tuirp Series, Vou. XIV, No. 80.—Aveust, 1877. 
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