554 Mr. C. W. Raffety on some Investigations of 



line is much fainter, while a third line — X 4293*26 — is 

 strong. This line appears to coincide with a faint line 

 in the flame spectrum, but its intensification in the case 

 of the aro-in-flame is as remarkable as is the reduction of 

 intensity of the line \4292'2. 



The recent announcement by Prof. Newall of the identifi- 

 cation of the hydrocarbon lines with those of the " Gr " group 

 in the solar spectrum has given a greatly increased interest 

 to the hydrocarbon spectrum ; and a further study of the 

 variations mentioned in this paper may yield important 

 information for the interpretation of the solar absorption 

 lines. If it should be possible to trace variations in the 

 lines of the " Gr" group depending on the particular region 

 of the sun from which the light is received, a comparison 

 with different laboratory spectra such as those herein de- 

 scribed might lead to definite conclusions as to temperature 

 and the probable location of the absorption. 



In the flame spectrum there are no lines between the 

 head of the band (about X 4315) and the isolated line 

 X 4324 ; but the arc-in-flame shows many lines in this 

 region. 



The author is indebted to Dr. W. Marshall Watts for his 

 kindness in making some preliminary measurements of the 

 spectrograms. The wave-lengths of the components of 

 " the three," as they occur in the normal arc, the arc-in- 

 flame, and the flame, and of the group of lines about X 4324 

 typical of the arc-in-flame, are as follows : — 



Normal Arc. Arc-in-flame. Flame. 



3 X 4381-65 4381*70 



80-67 4380-57 



3 2 4372-34 4372-33 



4370-74 70-74 70*77 



69-09 



3 3 4364-84 4364-84 4364-03 



4324-03 

 23-30 

 23-19 

 23-08 

 22-20 



4321-6 



(Wave-lengths on the International scale.) 



