Se ee eee ee Ee ee et ee oe eS es 
ae ee ee Te eR re ee eee ne eS ee Tene Fn amen cae IER TTT Mel rg ie Ae re POE RS Ae we Rap NT Tn eT ee ay aren ee 
J. C. Draper—Dark Lines of Oxygen in the Solar Spectrum. 449 
down to one-half its size by a photo-engraving operation. From 
the wee so produced, the diagram was printed. For accurate 
work the figures in the tables should be employed. 
The first space of the diagram beneath the scale of wave 
lengths gives the positions of the solar lines of Angstrém’s 
chart. 
The second represents measurements made from one of Dr. 
Rutherfurd’s paper prints of this region. These measurements 
were made after I received Mr. Christie’s paper, with a view to 
the detection of any difference between Dr. Rutherfurd’s photo- 
graph and m 
The third space contains a presentation of the lines of this 
region as given r. W. EL hristie, of the Royal Ob- 
servatory at Greenwich, in the Monthly Notices of J une, 1878. 
This I _ not receive until the latter part of last January, 
when much pleased to find the close coincidences of 
our egieca altboagl they were obtained by entirely different 
methods, and without any knowledge of each other's work. 
Line by line Mr, Christie’s map is the counterpart of the 
trum I had mapped from the photographs taken during the 
last week in November, and since that time. Not o only do 
these maps agree very closely in the placing of the lines, but 
the similarity in intensity is also marked. The presence of 
these faint lines in Mr. Christie’s prismatic spectrum sett 
the oxygen lines in the nenity of G. Deeiasioe below, “i 
gins gives a single line at 44318. ‘The other observers all 
Am, Jour, -_ “apae Vou. XVII, No. 102.—Junz, 1879, 
