438 PROF. F. W. DYSON: DETERMINATIONS OF WAVE-LENGTH FROM SPECTRA 
Hydrogen. 
In the following table a comparison is given of the measured wave-lengths of the 
hydrogen lines with those computed by the formula 
i 2 r i 
X = - —_ where a =---and is derived from Rowland’s values for H a , H^, H y 
a n 2 — 4 2741875 J 
and corrected for air :— 
Line. 
Intensity. 
Wave-length. 
Tabular. 
T - 0. 
S 
30 
4101-92 
1-90 
-0-02 
€ 
30 
3970-21 
0-22 
+ 0-01 
e. 
£ 
20 
3889-15 
9-20 
+ 0-05 
He line at 3888-7 2. 
V 
20 
3835-53 
5-53 
0-00 
6 
19 
3798-06 
8-04 
-0-02 
L 
15 
3770-79 
0-77 
-0-02 
K 
10 
3750-32 
0-30 
- 0-02 
X 
12 
3734-52 
4-51 
-0-01 
r 
12 
3722-05 
2-08 
+ 0-03 
V 
10 
3712-12 
2-11 
-0-01 
£ 
10 
3704-00 
4-00 
0-00 
o 
8 
3697-29 
7-29 
0-00 
8 
3691-70 
1-70 
o-oo 
p 
7 
3687-00 
6-97 
-0-03 
cr 
4 
3682-92 
2-95 
+ 0-03 
T 
3 
3679-50 
9-49 
-0-01 
V 
3 
3676-54 
6-50 
-0-04 
</> 
3 
3673-90 
3-90 
o-oo 
x 
3 
3671-46 
1-48 
+ 0-02 
Zr line at 3671 -41. 
2 
3669-58 
9-60 
+ 0-02 
to 
2 
3667-89 
7-82 
-0-07 
CL 
2 
3666-21 
6-24 
+ 0-03 
fl' 
3 
3664-78 
4-82 
+ 0-04 
Y line at 3664-76. 
y' 
2 
3663-58 
3-54 
-0-04 
S’ 
2 
3662-35 
2-40 
+ 0-05 
Ti line at 3662 • 38. 
/ 
€ 
i 
3661-39 
1-35 
-0-04 
The agreement with the formula is very close : there is a mean difference ol —'010 
which could be corrected by a slight change in the constant, but it is open to doubt 
whether this is a real difference. It seems that Balmer’s law for the hydrogen 
lines holds to within about '01 of a tenth-metre. 
Helium. 
The helium lines are strongly shown, but those of par-helium are doubtful. I here 
is a line at 4388'10 which may coincide with 438875, intensity 3. The line at 3964 
possibly occurs as a compound line. The lines at 5015 and 4922 are not shown. 
Argon, Xenon, Neon, Krypton. 
There is no evidence of the presence of these gases in the chromosphere. 
Carbon. 
A number of carbon lines including the heads of the band at 3833 are shown, but 
not very strongly. 
