PHENOMENA RELATING TO THE SPECTRA OF HYDROGEN AND HELIUM. 257 
the various wave-lengths characteristic of Helium. The total length of the wedge on 
the magnified photograph is 32 mm., and the values of D x , the density of the wedge, 
are obtained from the previous graph already described. 
Carbon Arc, H = 32 mm. 
A. 
K- 
D A/ H - 
Photographic 
intensity. 
Ratios to 
value for 3888. 
Absolute 
intensity ratio 
from previous ] 
table. 
7065 
17-3 
3-95 
2-135 
136-6 
13-7 
28-98 
6678 
23-8 
4-1 
3-049 
1120 
112-0 
28-00 
5876 
21-8 
4-5 
3-066 
1163 
116-3 
16-10 
5047 
16-7 
5-0 
2-603 
401 
40-1 
7-04 
5015 
17-0 
5-0 
2-656 
453 
45-3 
6-92 
4929 
18-5 
5-15 
2-977 
949 
94-9 
6-08 
4714 
19-2 
5-45 
3-270 
1863 
186-3 
4-475 
4472 
16-2 
5-9 
2-987 
970 
97-0 
3-02 
4438 
16-0 
6-0 
3-000 
1000 
100-0 
2-73 
4388 
14-4 
6-13 
2-758 
573 
57-3 
2-56 
4143 
10-1 
6-9 
2-178 
150-6 
15-06 
1-73 
4121 
9-9 
6-95 
2-026 
106-3 
10-63 
1-61 
4026 
7-4 
7-4 
1-711 
51-4 
5-14 
1-31 
3965 
5-7 
7-7 
1-372 
23-54 
2-35 
1-17 
3888 
4-0 
8-0 
1-000 
10-00 
1-00 
1-00 
It is evident from the last two columns that the photographic effect is a very 
complicated function of wave-length, and that the present method of using the same 
plate for the standard spectrum and that to be measured is the only one which can 
give quantitative values for intensity, with a real physical significance. 
Measurements of the ordinary spectrum of Helium on an adjacent portion of the 
same plate give the results shown in the next table. 
Helium (Ordinary Discharge), H = 32 mm. 
A. 
K 
W H - 
i 
Photographic 
intensity. 
A. 
K- 
WH. 
Photographic 
intensity. 
7065 
4-5 
0-555 
3-594 
4472 
13-8 
2-544 
350-2 
6678 
11-8 
1-512 
32-5 
4388 
5'5 
1 • 054 
11-3 
5876 
14-4 
2-025 
105-9 
4121 
30 
0-651 
4-48 
5044 
2-9 
0-453 
2-839 
4026 
5-4 
1-249 
17-7 
5015 
10-3 
1-609 
40-7 
3965 
3-0 
0-719 
5-23 
4932 
8-3 
1-336 
21-7 
3888 
8-0 
2-00 
100 
4714 
J 
10-5 
1 -788 
61-4 
The lines AA4438, 4143 are omitted, for they were too weak to admit of accurate 
measurement. 
