92 Henry Draper. 
Secchi into his great work on the sun, and in 1880 a lithograph 
of it was published in the Proceedings of the British Associa- 
tion as the most suitable reproduction extant, for determining 
the wave-length of the fixed lines. The spectrum was obtained 
with a Rutherfurd grating of 6481 lines to the inch, and in the 
photo-lithograph a portion of Angstrém’s drawing is repro- 
uced for comparison with it. In 1876 he succeeded in face 
of great difficulties, in photographing the solar spectrum and 
the spectrum of an incandescent gas upon the same plate with 
their edges in contact; thus admitting of accurate comparison 
between the lines. He then noticed that, while the lines of the 
iron and aluminum used as electrodes coincided exactly with 
to bright solar lines. He was led to conclude therefore, not 
only that oxygen actually existed in the sun, but that it existed 
there under conditions, probably of temperature, which caused 
it to radiate more light than the surrounding solar masses. At 
the same time therefore, that he announced his discovery of 
oxygen in the sun, he proposed an important modification in 
and early in 1879 produced a photograph of marvellous excel- 
ence on a much larger scale which showed the coincidences, 
especially of groups, so accurately as to leave no longer any 
doubt upon the subject. He was anxious, however, to obtain 
conditions which should make the lines of oxygen sharper; 
and had made special preparation for the accomplishment of 
this result during the present winter. 
While using the gelatino-bromide dry process in stellar 
spectrum photography, Dr. Draper conceived that the great 
sensitiveness of these plates might enable him to secure a pho- 
tograph of a nebula and so to obtain an accurate record of its 
resent condition with a view to future comparisons. On Sep- 
