408 PROF. F. W. DYSON: DETERMINATIONS OF WAVE-LENGTH FROM SPECTRA 
As regards the identification of the lines, Rowland’s Solar Spectrum was first 
compared with the chromospheric spectrum, and was, to a certain extent, a very good 
guide. Comparison with arc spectra— e.g., the titanium, chromium, &c., spectra of 
Hasselberg —was generally speaking a complete failure. Comparison was next made 
with Exner and Haschek’s Spark Spectra, and the great majority of the stronger 
lines of the chromospheric spectrum were at once seen to be strong spark-lines of 
titanium, chromium, scandium, yttrium, iron, manganese, and zirconium. 
It seemed desirable to give with the wave-lengths the intensities in the sun and in 
the spark, and for completeness the intensity in the arc is also given. The intensities 
in the sun were taken from Rowland, in the spark from Exner and Haschek, in 
the arc from Ivayser and Runge for iron, Ca, Mg, Al, &c. ; from Hasselberg for 
titanium, chromium, manganese, nickel and cobalt; from Rowland and Tatnall for 
zirconium, vanadium and lanthanum. The intensities in the arc spectra were revised 
and many additions to the intensities both in the arc and spark were afterwards 
made from Mr. Jewell’s discussion of his observations at Pinehurst (Publications of 
U.S. N aval Observatory, Washington, 1905). In the column giving the intensity in 
the arc, 0 denotes that the line is not found in the list with which comparison has been 
made to distinguish from —-, where no information has been found. I have not attempted 
to push the identification of the lines further than seemed reasonably probable. 
For the part of the spectrum from to D 3 , which depends entirely on photographs 
taken in Sumatra, I have given Mr. Lord’s results for comparison. The definition of 
my spectra in this part was not very good. 
si 
chro 
Wave¬ 
length. 
>ectrum 
of 
mospher 
No. of 
photos. 
e. 
Inten¬ 
sity. 
Element. 
Probabl 
Wave¬ 
length . 
e identification. 
Intensity. 
Spark. 
Are. 
Sun. 
3295-91 
1 
2 
— 
— 
— 
— 
— 
3302-98 
1 
2 
_ 
_ 
_ 
_ 
_ 
I 
J* Probably Na. 
.3303-48 
1 
1 
— 
— 
— 
— 
— 
J 
3313'92 
1 
0 
— 
— 
— 
— 
- 
.3321 -54 
1 
1 
— 
- 
- 
- 
— 
3323-00 
2 
2 
Ti 
3323-06 
30 
— 
5 
3324-14 
i 
0 
— 
3324-20 
- 
— 
4N 
3326-87 
i 
1 
Ti 
3.326 -91 
10 
- 
5 
3329"53 
2 
2 
Ti 
3329-57 
20 
— 
5 
3332-18 
2 
1 
Ti 
3332-24 
15 
— 
3 
3335-29 
2 
2 
Ti 
3335-30 
20 
— 
4 
3336‘51 
1 
1 
Cr 
3336-48 
8 
— 
3339-99 
1 
1 
Cr 
3339-99 
10 
— 
3 
3340-48 
2 
3 
Ti 
3340-46 
15 
— 
3 
3341 -98 
2 
4 
Ti 
3.341 -97 
20 
— 
4 
3342-72 
1 
1 
Cr 
3342-72 
10 
— 
3 
3.343-90 
1 
0 
Ti 
3343-91 
7 
3 
4 
3346-95 
1 
1 
Ti 
3346-90 
7 
8 
2 
P 
