448 J. 0. Draper—Dark Lines of Oxygen in the Solar Spectrum. 
“Art. LVIL—On the Dark Lines of Oxygen in the Solar Spectrum 
on the less refrangible side of G; by JOHN CHRISTOPHER 
Draper, M.D., LL.D., Professor of Natural History in the 
College of the City of New York. 
In a paper on the lines of oxygen, published in this Journal 
for October, 1878, the solar lines closely coincident with those 
of the electric spectrum of oxygen were given. The measure- 
ments of the solar lines in that instance were taken from photo- 
graphs made in March, 1878. Since that time, under more 
favorable atmospheric conditions, I have succeeded in obtain- 
ing finer photographs on the less refrangible side of G. These 
show many faint lines, not visible in the photographs of March 
1878, while many other lines are distinctly sub-divided. Three 
of the recent photographs were taken on the same day, during 
the last week in November, and two have been taken since that 
time; one during the last week in January, and one during the 
first week in February. In all five of these photographs faint 
lines are visible between 44316 and 44320, of Angtsrém’s 
scale, and they all show them in the position indicated by the 
diagram and table. The fact that all the photographs agree in 
their representation of these lines, is, I think, proof positive of 
the correctness of the positions assigned. 
| 
liens sek ad Scale of wave lengths. 
j { | | jAngstrém’s Chart lines. 
7 
TTT ETL [Ul ©] |ruthertura diffraction lines. 
i] Christie Prismatic lines. 
TUT UWE - ©. paper Dittraction lines. 
ctra. Solar Spectra. 
|_| 
= 4. Angstrém’s Chart. 
J. C. Draper. 
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| | H. Draper. : e 
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assistant, Mr. 
at the close of this article. The drawing was on the scale of 
One centimeter to each wave length. This was photographed 
