264 =o. C. Draper—Dark Lines in the Solar Spectrum. 
we have seen assignable to oxygen, in seventeen the coinci- 
dences are absolute; in four the difference is only five one- 
hundredths of a wave length ; in twenty-two, ten one-hundredths 
of a wave length; in four, fifteen one- -hundredths of a wave 
length; in eleven, twenty-one one-hundredths of a wave length, 
and in the remainder the greatest difference is only thirty-five one- 
hundredths of a wave length, or about that which Angstrom 
has made in different measurements of the same line in the 
solar spectrum. 
The small figure attached as a power to each wave length of 
the electric and solar spectra in the table, is a proximate ex- 
pression of the photographic strength of that particular line in 
each spectrum, and an examination of these upholds the state- 
ment made in a preceding paragraph that the oxygen lines 
of the solar spectrum are very weak when no other apa 
furnishes a line which falls on the same wave length. Ofco 
photographic must not be compared with visual intensities, fe 
as the one diminishes in the less song saa so of the 
— spectrum the other increases. Ane mple of coinci- 
dence in the lines of different ae mE and consequent incre- 
and electric spectra. From this table it will be seen that 
ngstrém himself observed a number of lines, the relations of 
which to elementary bodies no one has as yet demonstrated, 
and which I believe represent the oxygen in the solar envelopes. 
Table of free lines in Angstrém’s solar —- which may be 
attributed to oxygen 
Draper’s electric Draper’s solar Kpgurta’s wat’ solar 
spectrum of oxygen. spectrum. spectrum. 
4132-908 33° 
4155-754 4155°60! 4155-80? 
4254°50° 4254-30! 4 
3-004 4303-005 4303°00° 
4316°508 16°602 4316 
“30! 4348°20? 4347-95! 
4394-50% 4394°45? 
4595°403 4595°2 
4648°15!0 4648-154 4648-75 
4661°'504 4661-70? 
The subjects a in this communication may be briefly 
summed up as at 
‘. ane resort to the process of reflection in producing and 
