268 H. Draper— Oxygen in the Sun. 
under which the oxygen spectrum is seen when compared with 
the spark spectrum are modified. In fact, a critical study of 
the two spectra demands that each line of oxygen should be 
separately photographed with the corresponding region of the 
Sun’s spectrum, so as to reproduce as nearly as possible the 
same conditions for each. As an instance of the modifications 
continuation of this research is in that direction. But the sub- 
of the photosphere. The fact that oxygen, within a certaim 
range of variation, suffers less change than others of the nou- 
metals has been the secret of its rs in the Sun. 2 
a to have a greater stability of constitution, ‘hone 
Schuster has shown that its spectrum may be made to vary- 
have already begun an extended series of experiments on 
non-metals; but the results exhibit such confusion that thelr 
